ATA2-EIDE.txt

WORKING DRAFT   X3T10
proposed American National Standard     948D

        Revision 3
        January 17, 1995






Information technology -
AT Attachment Interface with Extensions
(ATA-2)



Committee Disclaimer

This is an internal working document of X3T10, a Technical Committee of
Accredited Standards Committee X3.  As such, this is not a completed standard.
The contents are actively being modified by X3T10.  This document is made
available for review and comment only.


Copyright Notice

Copyright 1994, Computer and Business Equipment Manufacturers Association.
Permission is granted to members of X3, its technical committees, and their
associated task groups to reproduce this document for the purposes of X3
standardization activities without further permission, provided this notice is
included.  All other rights are reserved.



ASC X3T10 Technical Editor:                     Stephen G. Finch
                                                        Silicon Systems, Inc.
                                                        14351 Myford Road
                Tustin, CA 92680-7022
                                                        USA

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                                                        Fax:    714-573-6914
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Reference number
ISO/IEC ***** : 199x
ANSI X3.*** - 199x
Printed March, 17, 1995 7:44AM



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ABSTRACT

The draft standard for AT Attachment Interface For Disk Drives has been
completed, but as the popularity of the interface has increased, its application
area has grown outside the originally intended purpose.  This draft proposed
standard is based upon the AT Attachment Interface For Disk Drives.  This
document is a stand alone document, separate from that document.  The ATA
Extensions (ATA-2) standard is intended to broaden the scope and application
area and take advantage of the huge installed BIOS (Basic Input/Output System)
base, and software.

This standard defines an integrated interface between devices and host
processors.  It provides a common point of attachment for systems manufacturers,
system integrators, and suppliers of intelligent devices.

The proposed ATA-2 standard shall maintain a high degree of compatibility with
the AT Attachment while providing documentation for new capabilities.  This
proposed standard is not intended to require changes to presently installed
devices or existing software.  It is intended that this proposed standard would
be used to provide additional capabilities.

The proposed ATA-2 standard involves evolutionary expansion of the draft AT
Attachment standard to provide additional capabilities.  The nature of the
proposed project is to insure that the AT Attachment has an upward, highly
compatible growth path.  This will insure that current investments in AT
Attachment are provided with more stability in the face of technological
developments.  It is likely that any isolated negative impacts would occur in
any case through non-standard evolution or revolution.


PATENT STATEMENT

CAUTION: The developers of this standard have requested that holder's of patents
that may be required for the implementation of the standard, disclose such
patents to the publisher.  However, neither the developers nor the publisher
have undertaken a patent search in order to identify which, if any, patents may
apply to this standard.

As of the date of publication of this standard and following calls for the
identification of patents that may be required for the implementation of the
standard, no such claims have been made.  No further patent search is conducted
by the developer or the publisher in respect to any standard it processes.  No
representation is made or implied that licenses are not required to avoid
infringement in the use of this standard.





Contents        Page
Foreword        9
Introduction    10
1. Scope        11
2. Normative references 11
3. Definitions, abbreviations and conventions   12
3.1. Definitions and Abbreviations      12
3.1.1. ATA (AT attachment)      12
3.1.2. ATA-1 device     12
3.1.3. AWG      12
3.1.4. Command acceptance       12
3.1.5. CHS (Cylinder-head-sector)       12
3.1.6. Data block       12
3.1.7. Device   12
3.1.8. Device selection 12
3.1.9. DMA (Direct memory access)       13
3.1.10. LBA (Logical block address)     13
3.1.11. Master  13
3.1.12. Optional        13
3.1.13. PIO (Programmed input/output)   13
3.1.14. Reserved        13
3.1.15. Sector  13
3.1.16. Slave   13
3.1.17. Unrecoverable error     13
3.1.18. VS (Vendor specific)    14
3.2. Conventions        14
3.2.1. Keywords 14
3.2.2. Numbering        14
3.2.3. Signal Conventions       14
3.2.4. Bit Conventions  15
3.2.5. Byte Ordering For 8-bit and 16-bit Data Transfers        15
4. Interface Physical and Electrical Requirements       16
4.1. Configuration      16
4.2. DC cable and connector     17
4.2.1. 4-pin power      17
4.3. I/O connector      18
4.4. I/O cable  18
4.5. Electrical Characteristics 19
4.5.1. ATA-2 Driver Types and Required Pull-ups 20
5. Interface Signal Assignments and Descriptions        21
5.1. Signal summary     21
5.2. Signal descriptions        22
5.2.1. CS0- (CHIP SELECT 0)     22
5.2.2. CS1- (CHIP SELECT 1)     22
5.2.3. DA2, DA1, and DA0 (DEVICE ADDRESS)       22
5.2.4. DASP- (Device active, device 1 present)  23
5.2.5. DD0-DD15 (Device Data)   23
5.2.6. DIOR- (Device I/O read)  23
5.2.7. DIOW- (Device I/O write) 23
5.2.8. DMACK- (DMA acknowledge) (Optional)      23
5.2.9. DMARQ (DMA request) (Optional)   24
5.2.10. INTRQ (Device interrupt)        24
5.2.11. IOCS16- (Device 16-bit I/O)     25
5.2.12. IORDY (I/O channel ready) (Optional)    25
5.2.13. PDIAG- (Passed diagnostics)     26
5.2.14. RESET- (Device reset)   26
5.2.15. SPSYNC:CSEL (Spindle synchronization/cable select) (Optional)   26
5.2.15.1. SPSYNC (Spindle synchronization) (Optional)   27
5.2.15.2. CSEL (Cable select) (Optional)        27
6. Interface Register Definitions and Descriptions      28
6.1. Device Addressing Considerations   28
6.2. I/O register descriptions  29
6.2.1. Alternate Status register        30
6.2.2. Command register 30
6.2.3. Cylinder High register   30
6.2.4. Cylinder Low register    30
6.2.5. Data register    30
6.2.6. Device Control register  31
6.2.7. Device/Head register     31
6.2.8. Error register   32
6.2.9. Features register        32
6.2.10. Sector Count register   33
6.2.11. Sector Number register  33
6.2.12. Status register 34
7. General Operational Requirements     36
7.1. Reset response     36
7.2. Sector Addressing  37
7.3. Power Management Feature Set       38
7.3.1. Power modes      38
7.3.2. Power Management Commands        38
7.3.3. Standby timer    39
7.3.4. Idle mode transition     39
7.3.5. Status   39
7.3.6. Power Mode transitions   40
7.3.7. Interface Capability For Power Modes     41
7.4. Removable media mode transitions   42
7.5. Status and Error posting   44
8.Command Descriptions  45
8.1.ACKNOWLEDGE MEDIA CHANGE (removable)        48
8.2.BOOT - POST-BOOT (removable)        49
8.3.BOOT - PRE-BOOT (removable) 50
8.4.CHECK POWER MODE    51
8.5.DOOR LOCK (removable)       52
8.6.DOOR UNLOCK (removable)     53
8.7.DOWNLOAD MICROCODE  54
8.8.EXECUTE DEVICE DIAGNOSTIC   55
8.9.FORMAT TRACK        57
8.10.IDENTIFY DEVICE    58
8.10.1.Word 0: General configuration    60
8.10.2.Word 1: Number of cylinders      60
8.10.3.Word 2: Reserved.        60
8.10.4.Word 3: Number of logical heads  60
8.10.5.Word 4: Vendor specific data.    60
8.10.6.Word 5: Vendor specific data.    60
8.10.7.Word 6: Number of logical sectors per logical track      61
8.10.8.Words 7-9: Vendor specific data. 61
8.10.9.Words 10-19: Serial Number       61
8.10.10.Word 20: Vendor specific data.  61
8.10.11.Word 21: Vendor specific data.  61
8.10.12.Word 22: Number of vendor specific bytes on READ/WRITE LONG
commands        61
8.10.13.Word 23-26: Firmware revision   61
8.10.14.Words 27-46: Model number       61
8.10.15.Word 47: READ/WRITE MULTIPLE support.   61
8.10.16.Word 48: Reserved.      61
8.10.17.Word 49: Capabilities   62
8.10.17.1.Standby Timer Support 62
8.10.17.2.IORDY Support 62
8.10.17.3.IORDY Can Be Disabled 62
8.10.17.4.LBA supported 62
8.10.17.5.DMA supported 62
8.10.18.Word 50: Reserved.      62
8.10.19.Word 51: PIO data transfer cycle timing mode    62
8.10.20.Word 52: Single Word DMA data transfer cycle timing mode        62
8.10.21.Word 53: Field Validity 63
8.10.22.Word 54: Number of current logical cylinders    63
8.10.23.Word 55: Number of current logical heads        63
8.10.24.Word 56: Number of current logical sectors per logical track    63
8.10.25.Word 57-58: Current capacity in sectors 63
8.10.26.Word 59: Multiple sector setting        63
8.10.27.Word 60-61: Total number of user addressable sectors    63
8.10.28.Word 62: Single word DMA transfer       63
8.10.29.Word 63: Multiword DMA transfer 64
8.10.30.Word 64: Flow Control PIO Transfer Modes Supported      64
8.10.31.Word 65: Minimum Multiword DMA Transfer Cycle Time Per Word     64
8.10.32.Word 66: Manufacturer's Recommended Multiword DMA Cycle Time    64
8.10.33.Word 67: Minimum PIO Transfer Cycle Time Without Flow Control   65
8.10.34.Word 68: Minimum PIO Transfer Cycle Time With IORDY     65
8.10.35.Words 69-70: Reserved for future PIO modes.     65
8.10.36.Words 71-127: Reserved. 65
8.10.37.Words 128-159: Vendor specific. 65
8.10.38.Words 160-255: Reserved.        65
8.11.IDLE       66
8.12.IDLE IMMEDIATE     67
8.13.INITIALIZE DEVICE PARAMETERS       68
8.14.MEDIA EJECT (removable)    69
8.15.NOP        70
8.16.READ BUFFER        71
8.17.READ DMA (with retries and without retries)        72
8.18.READ LONG (with retries and without retries)       73
8.19.READ MULTIPLE      74
8.20.READ SECTOR(S) (with retries and without retries)  75
8.21.READ VERIFY SECTOR(S) (with retries and without retries)   76
8.22.RECALIBRATE        77
8.23.SEEK       78
8.24.SET FEATURES       79
8.25.SET MULTIPLE MODE  81
8.26.SLEEP      82
8.27.STANDBY    83
8.28.STANDBY IMMEDIATE  84
8.29.WRITE BUFFER       85
8.30.WRITE DMA (with retries and without retries)       86
8.31.WRITE LONG (with retries and without retries)      87
8.32.WRITE MULTIPLE     88
8.33.WRITE SAME 89
8.34.WRITE SECTOR(S) (with retries and without retries) 90
8.35.WRITE VERIFY       91
9. Protocol     92
9.1. Power on and hardware resets       93
9.1.1. Power on and hardware resets - device 0  93
9.1.2. Power on and hardware resets - device 1  93
9.2. Software reset     94
9.2.1. Software reset - device 0        94
9.2.2. Software reset - device 1        94
9.3. PIO data in commands       96
9.4. PIO data out commands      98
9.5. Non-data commands  101
9.6. DMA data transfer commands (optional)      102
9.7. Device 0 only configurations       104
10. Timing      106
10.1. Deskewing 106
10.2. Symbols   106
10.3. Terms     106
10.4. Data Transfers    106
10.4.1. PIO Data Transfers      107
10.4.2. Single Word DMA Data Transfer   110
10.4.3. Multiword DMA Data Transfer     111
10.5. Power on and hard reset   113
Annex A. Diagnostic and reset considerations from a device firmware
standpoint      114
A.1. Power on and hardware reset (RESET-)       114
A.2. Software reset     114
A.3. Device diagnostic command  114
A.4. Truth table        114
A.5. Power on or hardware reset algorithm       115
A.5.1 Algorithm for Device 0    115
A.5.2 Algorithm for Device 1    116
A.6 Software Reset Algorithm    117
A.6.1 Algorithm for Device 0    117
A.6.2 Algorithm for Device 1    117
A.7.  Diagnostic Command Algorithm      118
A.7.1 Algorithm for Device 0    118
A.7.2 Algorithm for Device 1    118
Annex B. 44-Pin Small Form Factor Connector     119
B.1. 44-pin signal assignments  119
Annex C. 68-Pin Small Form Factor Connector     121
C.1. Overview   121
C.2. Signals    121
C.3. Signal Descriptions        122
C.3.1. CD1- (Card Detect 1)     123
C.3.2. CD2- (Card Detect 2)     123
C.3.3. CS1- (Device chip Select 1)      123
C.3.4. DMACK- (DMA Acknowledge) 123
C.3.5. DMARQ (DMA Request)      123
C.3.6. IORDY (I/O Channel Ready)        123
C.3.7. M/S- (Master/Slave)      123
C.3.8. SELATA- (Select 68-pin ATA)      123
C.4. Removability Considerations        124
C.4.1. Device Recommendations   124
C.4.2. Host Recommendations     124
Annex D.  Identify Device Data For ATA Devices Below 8 GB       125
D. Identify Drive Data Requirements     125
D.2 Cylinder, Head and Sector Addressing        125
D.2.1. Word 1   126
D.2.2. Word 3   126
D.2.3 Word 6    126
D.2.4 Use of words 53 through 58        126
D.2.5 Word 53   126
D.2.6 Word 54   127
D.2.7 Word 55   127
D.2.8 Word 56   127
D.2.9 Words 57-58       127
D.3 Logical Block Addressing    127
D.3.1 Words 60-61       127
D.3.2 Orphan Sectors    127
Annex E. ATA Command Set Summary        128



Figures Page
Figure 1 - ATA Interface Cabling Diagram        17
Figure 2 - Drive Side Connector Pin Numbering   17
Figure 3 - 40-Pin Connector Mounting    18
Figure 4 - Cable Select 27
Figure 5 - Power Management Modes       40
Figure 6 - Removable Modes      42
Figure 6 - Removable Modes (cont.)      43
Figure 7 - BSY and DRDY timing for Diagnostic command   56
Figure 8 - BSY and DRDY timing for power on and hardware resets 94
Figure 9 - BSY and DRDY timing for software reset       95
Figure 10 - PIO Data Transfer to/form Device (Part 1 of 2)      107
Figure 10 - PIO Data Transfer to/form Drive (Part 2 of 2)       109
Figure 11 - Single Word DMA Data Transfer       110
Figure 12 - Multiword DMA Data Transfer (Part 1 of 2)   111
Figure 12 - Multiword DMA Data Transfer (Part 2 of 2)   112
Figure 13 - Reset Sequence      113
Table 15 - Reset Error register Values  114

Tables  Page
Table 1 - DC Interface Using 4 Pin Power Connector      17
Table 2 - DC Characteristics    19
Table 3 - AC Characteristics    19
Table 4 - ATA-2 Driver Types and Required Pull-ups      20
Table 5 - Interface Signal Names and Pin Assignments    21
Table 6 - Interface signals description 22
Table 7 - I/O Port Functions and Selection Addresses    29
Table 8 - Power Conditions      41
Table 9 - Register Usage        44
Table 10 - Command Codes and Parameters 46
Table 11 - Diagnostic Codes     55
Table 12 - Identify Drive Information (Part 1 of 2)     59
Table 12 - Identify Drive Information (Part 2 of 2)     60
Table 13 - Automatic Standby Timer Periods      66
Table 14 - Set Features register Definitions    79
Table 15 - Automatic Standby Timer Periods      83
Table 16 - Signal Assignments for 44-Pin ATA    120
Table 17 - Signal Assignments for 68-Pin ATA    122
Table 18 - Command Matrix       128
Table 19 - Commands Sorted By Command Value (Part 1 of 2)       129
Table 19 - Commands Sorted By Command Value (Part 2 of 2)       130




Foreword


This standard encompasses the following:

Clause 1 describes the scope.

Clause 2 lists the normative references.

Clause 3 provides definitions, abbreviations and conventions used within
this document.

Clause 4 contains the electrical and mechanical characteristics; covering
the interface cabling requirements of the DC, data cables and connectors.

Clause 5 contains the signal descriptions of the AT Attachment Interface.

Clause 6 contains descriptions of the registers of the AT Attachment
Interface.

Clause 7 describes the general operating requirements of the AT Attachment
Interface.

Clause 8 contains descriptions of the commands of the AT Attachment
Interface.

Clause 9 contains an overview of the protocol of the AT Attachment
Interface.

Clause 10 contains the interface timing diagrams.

Annexes A through E are informative.






Introduction


When the first IBM PC(tm) (Personal Computer) was introduced, there was no hard
disk storage capability.  Successive generations of product resulted in the
inclusion of a hard disk as the primary storage device.  When the PC AT(tm) was
developed, a hard disk was the key to system performance, and the controller
interface became a de facto industry interface for the inclusion of hard disks
in PC ATs.

The price of desktop systems has declined rapidly because of the degree of
integration which reduced the number of components and interconnects.  A natural
outgrowth of this integration was the inclusion of controller functionality into
the hard disk.

In October 1988 a number of device suppliers formed the Common Access Method
Committee to encourage an industry-wide effort to adopt a common software
interface to dispatch input/output requests to SCSI devices.  Although this was
the primary objective, a secondary goal was to specify what was known as the AT
Attachment interface.  The resulting AT Attachment Interface For Disk Drives
standard fulfilled that requirement.

As personal computer type systems continued to evolve, there was a need to
extend the capabilities of the interface.  The lap-top and small computer
systems needed to modify the mechanical aspects of the interface.  High
performance systems needed to have enhanced transfer rates.  In addition, there
were a number of issues in the AT Attachment standard that needed to be
addressed.



1.      Scope

This standard extends the AT Attachment Interface with the addition of new
commands, and defining improved interface transfer rates.  In addition, general
improvements have been made in content for completeness and to improve clarity.

This standard defines the AT Attachment Interface.  This standard defines an
integrated interfaces between devices and host processors.  It provides a common
point of attachment for systems manufacturers, system integrators, and suppliers
of intelligent devices.

The application environment for the AT Attachment Interface is any device which
uses internal storage.

The PC AT Bus(tm) is a widely used and implemented interface for which a variety
of devices have been manufactured.  As a means of reducing size and cost, a
class of products has emerged which embed the controller functionality in the
device.  Because of their compatibility with existing AT hardware and software
this interface quickly became a de facto industry standard.  While the AT
Attachment Interface has its roots in the PC AT Bus(tm), its use has extended to
many other systems.

2.      Normative references

None.




3.      Definitions, abbreviations and conventions

3.1.    Definitions and Abbreviations

For the purposes of this International Standard, the following definitions
apply.

3.1.1.  ATA (AT attachment)

ATA defines the physical, electrical, transport, and command protocols for the
internal attachment of block storage devices.

3.1.2.  ATA-1 device

A device which complies with X3.221-1994, the AT Attachement Interface for Disk
Drives.

3.1.3.  AWG

American Wire Gauge.

3.1.4.  Command acceptance

A command is considered accepted whenever the host writes to the Command
Register and the device currently selected has its BSY bit equal to zero.  An
exception exists for the EXECUTE DIAGNOSTIC command (see the description of the
EXECUTE DIAGNOSTIC command).

3.1.5.  CHS (Cylinder-head-sector)


This term defines the addressing of the device as being by cylinder number, head
number and sector number.

3.1.6.  Data block

This term describes a unit of data words transferred using PIO data transfer. A
data block is transferred between the host and the device as a complete unit.  A
data block is a sector, except for data blocks of a READ MULTIPLE, WRITE
MULTIPLE, READ LONG and WRITE LONG commands.  In the cases of READ MULTIPLE and
WRITE MULTIPLE commands, the size of the data block may be changed in multiples
of sectors by the SET MULTIPLE MODE command.  In the cases of READ LONG and
WRITE LONG, the size of the data block is a sector plus a vendor specific number
of bytes.  The default length of the vendor specific bytes associate with the
READ LONG and WRITE LONG commands is four bytes, but may be changed by use of
the SET FEATURES command.

3.1.7.  Device

Device is a storage peripheral.  Traditionally, a device on the ATA interface
has been a hard disk drive, but any form of storage device may be placed on the
ATA interface provided it adheres to this standard.

3.1.8.  Device selection

A device is selected when the DEV bit of the Drive/Head register is equal to the
device number assigned to the device by means of a Device 0/Device 1 jumper or
switch, or use of the CSEL signal.

3.1.9.  DMA (Direct memory access)

A means of data transfer between device and host memory without processor
intervention.

3.1.10. LBA (Logical block address)

This term defines the addressing of the device as being by the linear mapping of
sectors.

3.1.11. Master

Previous to this standard, Device 0 has also been referred to as the master.
Through out this document the term Device 0 shall be used.

3.1.12. Optional

This term describes features which are not required by the standard.  However,
if any optional feature defined by the standard is implemented, it shall be done
in the way defined by the standard.  Describing a feature as optional in the
text is done to assist the reader.

3.1.13. PIO (Programmed input/output)

A means of accessing device registers.  PIO is also used to describe one form of
data transfers.  PIO data transfers are performed by the host processor
utilizing PIO register accesses to the Data register.

3.1.14. Reserved

Reserved  bits, bytes, words, fields and code values are set aside for future
standardization.  Their use and interpretation may be specified by future
extensions to this or other standards.  A reserved bit, byte, word or field
shall be set to zero, or in accordance with a future extension to this standard.
The recipient shall not check reserved bits, bytes, words or fields.  Receipt of
reserved code values in defined fields shall be treated as an error.

[Editor's note:  Look carefully at this as it may be considered by some to be a
technical change!

3.1.15. Sector

A uniquely addressable set of 256 words (512 bytes).

3.1.16. Slave

Previous to this standard, Device 1 has also been referred to as the slave.
Through out this document the term Device 1 shall be used.

3.1.17. Unrecoverable error

An unrecoverable error is defined as having occurred at any point when the
device sets either the ERR bit or the DF bit to one and the BSY bit to zero in
the Status register when processing of a command.



3.1.18. VS (Vendor specific)

This term is used to describe bits, bytes, fields and code values which are
reserved for vendor specific purposes.  These bits, bytes, fields and code
values are not described in this standard, and may be used in a way that varies
between vendors.  This term is also applied to levels of functionality whose
definition is left to the vendor.

3.2.    Conventions

If there is a conflict between text and tables, the table shall be accepted as
being correct.

3.2.1.  Keywords

Lower case is used for words having the normal English meaning.  Certain words
and terms used in this International Standard have a specific meaning beyond the
normal English meaning.  These words and terms are defined either in clause 3 or
in the text where they first appear.

The names of abbreviations, commands, fields, and acronyms used as signal names
are in all uppercase (e.g., IDENTIFY DEVICE).  Fields containing only one bit
are usually referred to as the "name" bit instead of the "name" field.  (See
Clause 3.2.4 for the naming convention used for naming bits.)

Names of device registers begin with a capital letter (e.g., Cylinder Low
register).

3.2.2.  Numbering

Numbers that are not immediately followed by a lower-case "b" or "h" are decimal
values.  Numbers that are immediately followed by a lower-case "b" (e.g., 01b)
are binary values.  Numbers that are immediately followed by a lower-case "h"
(e.g., 3Ah) are hexadecimal values.

3.2.3.  Signal Conventions

Signal names are shown in all upper case letters.

All signals are either high active or low active signals.  A dash character (-)
at the end of a signal name indicates it is a low active signal.  A low active
signal is true when it is below ViL, and is false when it is above ViH.  No dash
at the end of a signal name indicates it is a high active signal.  A high active
signal is true when it is above ViH, and is false when it is below ViL.

Asserted means that the signal is driven by an active circuit to its true state.

Negated means that the signal is driven by an active circuit to its false state.

Released means that the signal is not actively driven to any state.  Some
signals have bias circuitry that pull the signal to either a true state or false
state when no signal driver is actively asserting or negating the signal.  These
cases are noted under the description of the signal, and their released state is
stated.

Control signals that may be used for two mutually exclusive functions are
identified with their two names separated by a colon e.g.  SPSYNC:CSEL can be
used for either the Spindle Sync (SPSYNC) or the Cable Select (CSEL) functions.


3.2.4.  Bit Conventions

Bit names are shown in all upper case letters except where a lower case n
precedes a bit name.  If there is no preceding n, then when BIT is equal to one
the meaning of the bit is true, and when BIT is equal to zero the meaning of the
bit is false.  If there is a preceding n, then when nBIT is equal to zero the
meaning of the bit is true and when nBIT is equal to one the meaning of the bit
is false.

3.2.5.  Byte Ordering For 8-bit and 16-bit Data Transfers

Assuming a block of data contains "n" bytes of information, and the bytes are
labeled Byte(0) through Byte(n-1), where Byte(0) is first byte of the field, and
Byte(n-1) is the last byte of the block.

When such a block of data is transferred on the ATA interface in 16 bit wide
transfer mode, then the bytes shall be presented in the following order:

                 DD DD DD DD DD DD DD DD   DD DD DD DD DD DD DD DD
                 15 14 13 12 11 10 09 08   07 06 05 04 03 02 01 00
First transfer   --------Byte(1)--------   --------Byte(0)--------
Second transfer  --------Byte(3)--------   --------Byte(2)--------
...
Last transfer    -------Byte(n-1)-------   -------Byte(n-2)-------

When such a block of data is transferred on the ATA interface in 8 bit wide
transfer mode, then the bytes shall be presented in the following order:

                      DD DD DD DD DD DD DD DD
                          07 06 05 04 03 02 01 00
First transfer        --------Byte(0)--------
Second transfer       --------Byte(1)--------
...
Next to last transfer -------Byte(n-2)-------
Last transfer         -------Byte(n-1)-------

Note:  The above description is for data on the ATA Interface.  Host systems
and/or host adapters may cause the order of data, as seen in the memory of the
host, to be different.




4.      Interface Physical and Electrical Requirements

The traditional 40-pin ATA interface is documented in this section as one of the
connection schemes being utilized.  Annex B and Annex C provide a basic
definition of two alternative connection schemes.

4.1.    Configuration

This standard defines the ATA interface containing a single host or host adapter
and one or two devices.  If two devices are connected to the interface, they are
connected in a daisy chained configuration.  One device is configured as Device
0 and the other device as Device 1.

The designation of a device as Device 0 or Device 1 may be made in a number of
ways:

             - a switch or a jumper on the device
             - use of the Cable Select (CSEL) pin


                      +---------+
                      | Host or |-------+------------+
                      | Adapter |       |            |
                      +---------+  +----+-----+ +----+-----+
                                   | Device 0 | | Device 1 |
                                   +----------+ +----------+

                      +---------+
                      | Host or |-------+------------+
                      | Adapter |       |            |
                      +---------+  +----+-----+ +----+-----+
                                   | Device 1 | | Device 0 |
                                   +----------+ +----------+

In a two drive configuration, the order of placement of Device 0 and Device 1 on
the ATA interface cable is not significant to the operation of the interface.

                      +---------+
                      | Host or |-------+------------+
                      | Adapter |       |            |
                      +---------+               +----+-----+
                                                | Device   |
                                                +----------+

If only a single device is attached via the ATA interface to a host, it is
recommended that the host and the device be placed at the two ends of the cable.

Figure 1 - ATA Interface Cabling Diagram

Also see clause 5.2.15.2 on CSEL operation.



4.2.    DC cable and connector

The device receives DC power through a 4-pin connector.

4.2.1.  4-pin power

The pin assignments are shown in table 1.  Recommended part numbers for the
mating connector to 18 AWG cable are shown below, but compatible parts may be
used.

          Connector (4 pin)             AMP 1-480424-0 or compatible.
          Contacts (loose piece)        AMP 60619-4 or compatible.
          Contacts (strip)              AMP 61117-4 or compatible.

[Editor's Note:  Are these the device side connectors or the cable side
connectors?  Attempt to get diagrams from SFF-8012.]
[Editor's Note:  Does anyone else feel uneasy about specifying a manufacturer's
part number?  What if the manufacturer changes its specification for that part?
As far as I know they are under no obligation to tell us.  I know the history,
keep it simple and get the ATA specification out, but does this approach apply
to ATA-2 as well?]


                    +========================+============+
                    | Power line designation | Pin Number |
                    +========================+============+
                    |        +12 Volts       |     1      |
                    +------------------------+------------+
                    |     +12 Volt Return    |     2      |
                    +------------------------+------------+
                    |      +5 Volt Return    |     3      |
                    +------------------------+------------+
                    |         +5 Volts       |     4      |
                    +------------------------+------------+

Table 1 - DC Interface Using 4 Pin Power Connector


                 /----------+-----------+-----------+---------\
                /      4    |     3     |     2     |    1     \
                |   +5VDC   |+5V Return |+12V Return|  +12VDC  |
                +-----------+-----------+-----------+----------+

Figure 2 - Drive Side Connector Pin Numbering



[Editor's note:  4.3 Ground connection was deleted, subject to no objections.]

4.3.    I/O connector

The I/O connector is a 40-pin connector as shown in figure 3, with pin
assignments as shown in table 5.  The connector should be keyed to prevent the
possibility of installing it upside down.  A key is provided by the removal of
pin 20.  The corresponding pin on the cable connector should be plugged.

The pin locations are governed by the cable plug, not the receptacle.  The way
in which the receptacle is mounted on the printed circuit board affects the pin
positions, and pin 1 should remain in the same relative position.  This means
the pin numbers of the receptacle may not reflect the conductor number of the
plug.  The header receptacle is not polarized, and all the signals are relative
to pin 20, which is keyed.

By using the plug positions as primary, a straight cable can connect devices.
As shown in figure 3, conductor 1 on pin 1 of the plug has to be in the same
relative position no matter what the receptacle numbering looks like.  If
receptacle numbering was followed, the cable would have to twist 180 degrees
between a device with top-mounted receptacles, and a device with bottom-mounted
receptacles.


           +-----------------------+
           |                      1|
           |40         20         2|
         ======= Circuit board =======       ======= Circuit board =======
                                               |                      1|
                                               |40         20         2|
                                               +-----------------------+

Figure 3 - 40-Pin Connector Mounting



Recommended part numbers for the mating connector are shown below, but
equivalent parts may be used.

     Connector (40 pin)                 3M 3417-7000 or equivalent.
     Strain relief                      3M 3448-2040 or equivalent.

4.4.    I/O cable

The cable specifications affect system integrity and the maximum length that can
be supported in any application.

     Flat cable (stranded 28 AWG)       3M 3365-40 or equivalent.
     Flat cable (stranded 28 AWG)       3M 3517-40 (shielded) or equivalent.

Cable total length shall not exceed  0,46m (18 inches).

Cable capacitance shall not exceed 35 pf.




4.5.    Electrical Characteristics

Interface signal are defined in Table 2 and Table 3.

          +--------------------------------------+-----------+------------+
          | Description                          |  Min      |   Max      |
   +------+--------------------------------------+-----------+------------+
   | IoL  | Driver sink current                  | 12mA      |            |
   | IoH  | Driver source current                |400uA      |            |
   | Vih  | Voltage Input High                   | 2,0 V D.C.|            |
   | Vil  | Voltage Input Low                    |           |  0,8 V D.C.|
   | Voh  | Voltage Output High (Ioh = -400 u A) | 2,4 V D.C.|            |
   | Vol  | Voltage Output Low (Iol = 12ma)      |           |  0,5 V D.C.|
   +------+--------------------------------------+-----------+------------+
Table 2 - DC Characteristics



             +--------------------------------------------+------+--------+
             | Description                                |  Min |   Max  |
    +--------+--------------------------------------------+------+--------+
    |  tRISE | Rise time for any signal on AT interface(1)|  5ns |        |
    |  tFALL | Fall time for any signal on AT interface(1)|  5ns |        |
    |  Cin   | Input Capacitance(each host or Device)     |      |  25 pf |
    |  Cout  | Output Capacitance(each host or Device)    |      |  25 pf |
    +--------+--------------------------------------------+------+--------+
    (1)  tRISE and tFALL are measured from 10-90% of full signal amplitude
         with a total capacitive load of 100 pf.

Table 3 -  AC Characteristics


Note:  IoH value at 400 uA is insufficient in the case of DMARQ which is
typically pulled low by a 5.6k ohm resistor.




4.5.1.  ATA-2 Driver Types and Required Pull-ups

      +==============+========+========+=========+==========+========+
      |              |        | Driver | Pull-up | Pull-up  |        |
      | Signal       | Source | Type   | at Host | at each  | Notes  |
      |              |        |  (1)   |   (2)   | Device(2)|        |
      +--------------+--------+--------+---------+----------+--------+
      |              |        |        |         |          |        |
      | Reset        | Host   |  TP    |         |          |        |
      | DD 0:15      | Bidir. |  TS    |         |          |        |
      | DMARQ        | Device |  TS    | 5.6K PD |          | (3)    |
      | DIOR-  DIOW- | Host   |  TS    |         |          |        |
      | IORDY        | Device |  TS    |  1.0K   |          | (4)    |
      | SPSYNC/CSEL  |        |        |         |          | (5)    |
      |    CSEL      | Host   |        | Ground  |   10K    | (6)    |
      |    SPSYNC    | Device |  TS/OC |         |   VS     | (7)    |
      | DMACK-       | Host   |  TP    |         |          |        |
      | INTRQ        | Device |  TS    |         |          |        |
      | IOCS16-      | Device |  OC    |  1.0K   |          |        |
      | DA0:2        | Host   |  TP    |         |          |        |
      | PDIAG-       | Device |  TS    |         |   10K    |        |
      | CS0- CS1-    | Host   |  TP    |         |          |        |
      | DASP-        | Device |  OC    |         |   10K    | (5)    |
      |              |        |        |         |          |        |
      +==============+========+========+=========+==========+========+
(1) TS=Tri-State; OC=Open Collector; TP=Totem-Pole; PU=Pull-up;
PD=Pull-down; VS=Vendor specific
(2) All resistor values are minimum (lowest) allowed.
(3) ATA-2 defines this line to be tri-stated whenever the device is
not selected or is not executing a DMA data transfer.  When enabled
by DMA transfer, it shall be driven high and low by the device.
(4) This signal should only be enabled during DIOR/DIOW cycles to
the selected device.
(5) See signal descriptions for information on dual use of this
signal.
(6) When used as CSEL, Line is grounded at Host and 10K Pull-up is
required at both devices.
(7) When used as SPSYNC, application is vendor specific.

Table 4 - ATA-2 Driver Types and Required Pull-ups




5.      Interface Signal Assignments and Descriptions

5.1.    Signal summary

The physical interface consists of receivers and drivers communicating through a
40-conductor flat ribbon non-shielded cable using an asynchronous interface
protocol.  The pin numbers and signal names are shown in table 5.  Reserved
signals shall be left unconnected.  Table 6 contains an alphabetical listing by
pin acronym.

+===========================================+=============+====+=============+
| Description                               | Source      |Pin | Acronym     |
+-------------------------------------------+-------------+----+-------------+
| Reset                                     | Host        |  1 | RESET-      |
|                                           | n/a         |  2 | Ground      |
| Data bus bit 7                            | Host/Device |  3 | DD7         |
| Data bus bit 8                            | Host/Device |  4 | DD8         |
| Data bus bit 6                            | Host/Device |  5 | DD6         |
| Data bus bit 9                            | Host/Device |  6 | DD9         |
| Data bus bit 5                            | Host/Device |  7 | DD5         |
| Data bus bit 10                           | Host/Device |  8 | DD10        |
| Data bus bit 4                            | Host/Device |  9 | DD4         |
| Data bus bit 11                           | Host/Device | 10 | DD11        |
| Data bus bit 3                            | Host/Device | 11 | DD3         |
| Data bus bit 12                           | Host/Device | 12 | DD12        |
| Data bus bit 2                            | Host/Device | 13 | DD2         |
| Data bus bit 13                           | Host/Device | 14 | DD13        |
| Data bus bit 1                            | Host/Device | 15 | DD1         |
| Data bus bit 14                           | Host/Device | 16 | DD14        |
| Data bus bit 0                            | Host/Device | 17 | DD0         |
| Data bus bit 15                           | Host/Device | 18 | DD15        |
| Ground                                    | n/a         | 19 | Ground      |
| (keypin)                                  | n/a         | 20 | Reserved    |
| DMA Request                               | Device      | 21 | DMARQ       |
| Ground                                    | n/a         | 22 | Ground      |
| I/O Write                                 | Host        | 23 | DIOW-       |
| Ground                                    | n/a         | 24 | Ground      |
| I/O Read                                  | Host        | 25 | DIOR-       |
| Ground                                    | n/a         | 26 | Ground      |
| I/O Ready                                 | Device      | 27 | IORDY       |
| Spindle Sync or Cable Select              | (note 1)    | 28 | SPSYNC:CSEL |
| DMA Acknowledge                           | Host        | 29 | DMACK-      |
| Ground                                    | n/a         | 30 | Ground      |
| Interrupt Request                         | Device      | 31 | INTRQ       |
| 16 Bit I/O                                | Device      | 32 | IOCS16-     |
| Device Address Bit 1                      | Host        | 33 | DA1         |
| PASSED DIAGNOSTICS                        | (note 1)    | 34 | PDIAG-      |
| Device Address Bit 0                      | Host        | 35 | DAO         |
| Device Address Bit 2                      | Host        | 36 | DA2         |
| Chip Select 0                             | Host        | 37 | CS0-        |
| Chip Select 1                             | Host        | 38 | CS1-        |
| Device Active or Slave (Device 1) Present | (note 1)    | 39 | DASP-       |
| Ground                                    | n/a         | 40 | Ground      |
+-------------------------------------------+-------------+----+-------------+
| Note 1: See signal descriptions for information on source of these signals |
+============================================================================+
Table 5 - Interface Signal Names and Pin Assignments



               +=========+=========+        +=========+=========+
               | Signal  | Pin     |        | Signal  | Pin     |
               +---------+---------+        +---------+---------+
               | CS0-    | 37      |        | DD12    | 12      |
               | CS1-    | 38      |        | DD13    | 14      |
               | DA0     | 35      |        | DD14    | 16      |
               | DA1     | 33      |        | DD15    | 18      |
               | DA2     | 36      |        | DIOR-   | 25      |
               | DASP-   | 39      |        | DIOW-   | 23      |
               | DD0     | 17      |        | DMACK-  | 29      |
               | DD1     | 15      |        | DMARQ   | 21      |
               | DD2     | 13      |        | INTRQ   | 31      |
               | DD3     | 11      |        | IOCS16- | 32      |
               | DD4     |  9      |        | IORDY   | 27      |
               | DD5     |  7      |        | PDIAG-  | 34      |
               | DD6     |  5      |        | RESET-  |  1      |
               | DD7     |  3      |        | SPSYNC: | 28      |
               | DD8     |  4      |        | CSEL    | 28      |
               | DD9     |  6      |        | keypin  | 20      |
               | DD10    |  8      |        | ground  | 2,19,22,|
               | DD11    | 10      |        |         |24,26,30,|
               |         |         |        |         |40       |
               +=========|=========|        |=========|=========|

Table 6 - Interface signals - Alphabetical Listing


5.2.    Signal descriptions

5.2.1.  CS0- (CHIP SELECT 0)

This is the chip select signal from the host used to select the Command Block
Registers.  See Table 7.

Note:  This signal has also been known in the industry as CS1FX-.

5.2.2.  CS1- (CHIP SELECT 1)

This is the chip select signal from the host used to select the Control Block
Registers.  See Table 7.

Note:  This signal has also been known in the industry as CS3FX-.

5.2.3.  DA2, DA1, and DA0 (DEVICE ADDRESS)

This is the 3-bit binary coded address asserted by the host to access a register
or data port in the device.  See Table 7.

5.2.4.  DASP- (Device active, device 1 present)

This is a time-multiplexed signal which indicates that a device is active, or
that Device 1 is present.  This signal shall be an open collector output and
each device shall have a 10K ohm pull-up resistor.

During power on initialization or after RESET- is negated, DASP- shall be
deasserted by both Device 0 and Device 1 within 1 msec, and then Device 1 shall
assert DASP- within 400 msec to indicate that Device 1 is present.

Device 0 shall allow up to 450 msec for Device 1 to assert DASP-.

DASP- shall be negated following acceptance of a command by Device 1 or after 31
seconds, whichever comes first.

Any time after negation of DASP-, either device may assert DASP- to indicate
that a device is active.

If the host connects to the DASP- signal for the illumination of an LED or for
any other purpose, the host shall ensure that the signal level seen on the ATA
interface for DASP- shall maintain Voh and Vol compatibility, given the Ioh and
Iol requirements of the DASP- device drivers.

5.2.5.  DD0-DD15 (Device Data)

This is an 8- or 16-bit bi-directional data interface between the host and the
device.  The lower 8 bits are used for 8-bit transfers e.g.  registers, vendor
specific bytes associated with the READ LONG and WRITE LONG commands and, if the
device supports the Features register capability to enable 8-bit-only data
transfers (see clause 8.24, Set Features).

5.2.6.  DIOR- (Device I/O read)

This is the read strobe signal from the host.  The falling edge of DIOR- enables
data from a register or data port of the device onto the signals, DD0-DD7 or
DD0-DD15.  The rising edge of DIOR- latches data at the host and the host shall
not act on the data until it is latched.

5.2.7.  DIOW- (Device I/O write)

This is the Write strobe signal from the host.  The rising edge of DIOW- latches
data from the signals, DD0-DD7 or DD0-DD15, into a register or the data port of
the device.  The device shall not act on the data until it is latched.

5.2.8.  DMACK- (DMA acknowledge) (Optional)

This signal shall be used by the host in response to DMARQ to initiate DMA
transfers.

NOTE:  This signal may be negated by the Host to suspend the DMA transfer
in process.  For Multi-Word DMA transfers, the Device may negate DMARQ
within the tL specified time (refer to Figure 12) once DMACK- is asserted
and reassert it again at a later time to resume the DMA operation.
Alternatively, if the device is able to continue the transfer of data, the
device may leave DMARQ asserted and wait for the host to reassert DMACK-.

5.2.9.  DMARQ (DMA request) (Optional)

This signal, used for DMA data transfers between host and device, shall be
asserted by the device when it is ready to transfer data to or from the host.
The direction of data transfer is controlled by DIOR- and DIOW-.  This signal is
used in a handshake manner with DMACK- i.e.  the device shall wait until the
host asserts DMACK- before negating DMARQ, and re-asserting DMARQ if there is
more data to transfer.

This line shall be released (high impedance state) whenever the device is not
selected or is selected and no DMA command is in progress.  When enabled by DMA
transfer, it shall be driven high and low by the device.

When a DMA operation is enabled, IOCS16-, CS0- and CS1- shall not be asserted
and transfers shall be 16-bits wide.

NOTE:  In ATA-1 devices, this signal was either totem-pole or tri-state in
different implementations.  In EISA systems, 5.6K pull-down is used to
cause a logic low on undriven lines.  ATA-2 defines this line to be in
high-impedance mode except when DMA transfer is active from the selected
device.

In systems which may use mixed devices where totem-pole drivers are used, and
the system shares this line with other non-ATA devices, the ATA host or ATA
adapter shall ensure that appropriate protection is employed to protect ATA
device DMARQ drivers from damage.

5.2.10. INTRQ (Device interrupt)

This signal is used to interrupt the host system.  INTRQ is asserted only when
the device has a pending interrupt, the device is selected, and the host has
cleared the nIEN bit in the Device Control register.  If the nIEN bit is equal
to one, or the device is not selected, this output is in a high impedance state,
regardless of the presence or absence of a pending interrupt.

The interrupt pending condition shall be cleared by:
    -   assertion of RESET- or
    -   the setting of the SRST bit of the Device Control register, or
    -   the host writing the Command register or
    -   the host reading the Status register

On PIO transfers, INTRQ is asserted at the beginning of each data block to be
transferred.  A data block is typically a single sector, except when declared
otherwise by use of the SET MULTIPLE MODE command.  An exception occurs on
FORMAT TRACK, WRITE SECTOR(S), WRITE BUFFER and WRITE LONG commands - INTRQ
shall not be asserted at the beginning of the first data block to be
transferred.

On DMA transfers, INTRQ is asserted only once, after the command has completed.

If the system shares this line with non-ATA devices, the ATA host or ATA adapter
shall ensure that appropriate protection is employed to protect ATA device INTRQ
drivers from damage.

5.2.11. IOCS16- (Device 16-bit I/O)

During PIO transfer modes 0, 1 or 2, IOCS16- indicates to the host system that
the 16-bit data port has been addressed and that the device is prepared to send
or receive a 16-bit data word.  This shall be an open collector output.

*       When transferring in any PIO mode and accessing any register except the
data port, transfers shall be 8-bit using DD0-7.
*       When transferring in PIO modes 0, 1 or 2, if IOCS16- is not asserted,
transfers shall be 8-bit using DD0-7.
*       When transferring in PIO modes 0, 1 or 2, if IOCS16- is asserted,
transfers shall be 16-bit using DD0-15.
*       When transferring in PIO modes 3 or 4, IOCS16- shall not be used by the
host, and all transfers shall be 16-bit using DD0-15, except for bytes
beyond the 512th byte for READ LONG and WRITE LONG commands which shall
be 8-bit using DD0-7.
*       When transferring in DMA mode, the host shall use a 16-bit DMA channel
and IOCS16- shall not be asserted.

5.2.12. IORDY (I/O channel ready) (Optional)

This signal is negated to extend the host transfer cycle of any host register
access (Read or Write) when the device is not ready to respond to a data
transfer request.

If actively asserted, this signal shall only be enabled during DIOR-/DIOW-
cycles to the selected device. If open collector, when IORDY is not negated, it
shall be in the high-impedance (undriven) state.

The use of IORDY is required for PIO modes 3 and above.


5.2.13. PDIAG- (Passed diagnostics)

This signal shall be asserted by Device 1 to indicate to Device 0 that it has
completed diagnostics.  A 10K ohm pull-up resistor shall be used on this signal
by each device.

Following a power on reset, software reset or RESET-, Device 1 shall negate
PDIAG- within 1 msec (to indicate to Device 0 that it is busy).  Device 1 shall
then assert PDIAG- within 30 seconds to indicate that it is no longer busy, and
is able to provide status.  If Device 1 is present, then Device 0 shall wait for
up to 31 seconds from power-on reset, software reset or RESET- for Device 1 to
assert PDIAG-.  If Device 1 fails to assert PDIAG-, Device 0 shall set bit 7 to
1 in the Error register to indicate that Device 1 failed.  After the assertion
of PDIAG-, Device 1 may be unable to accept commands until it has finished its
reset procedure and is Ready (the DRDY bit is equal to one).

Following the receipt of a valid EXECUTE DEVICE DIAGNOSTIC command, Device 1
shall negate PDIAG- within 1 msec to indicate to Device 0 that it is busy and
has not yet passed its device diagnostics.  Device 1 shall then assert PDIAG-
within 5 seconds to indicate that it is no longer busy, and is able to provide
status.  Device 1 should clear the BSY bit before asserting PDIAG-.  If Device 1
is present then Device 0 shall wait for up to 6 seconds from the receipt of a
valid EXECUTE DEVICE DIAGNOSTIC command for Device 1 to assert PDIAG-.  If
Device 1 fails to assert PDIAG-, Device 0 shall set bit 7 to 1 in the Error
register to indicate that Device 1 failed.

If DASP- was not asserted by Device 1 during reset initialization, Device 0
shall post its own status immediately after it completes diagnostics, and clear
the Device 1 Status register to 00h.  Device 0 may be unable to accept commands
until it has finished its reset procedure and is Ready (the DRDY bit is equal to
one).

It is recommended that the host make no connect to the PDIAG- signal.

5.2.14. RESET- (Device reset)

This signal from the host system shall be asserted beginning with the
application of power and held asserted until at least 25 usec after voltage
levels have stabilized within tolerance during power on and negated thereafter
unless some event requires that the device(s) be reset following power on.

5.2.15. SPSYNC:CSEL (Spindle synchronization/cable select) (Optional)

This signal shall have a 10K ohm pull-up resistor.

This is a dual purpose signal and neither, either or both functions may be
implemented.  If both functions are implemented then they cannot be active
concurrently: the choice as to which is active is vendor specific.

All devices connected to the same cable should have the same function active at
the same time.  If SPSYNC and CSEL are mixed on the same cable, then device
behavior is undefined.

Prior to the introduction of this standard, this signal was defined as DALE
(Device Address Latch Enable), and used for an address valid indication from the
host system.  If used, the host address and chip selects, DAO through DA2, CS0-,
and CS1- were valid at the negation of this signal and remained valid while DALE
was negated, therefore, the device did not need to latch these signals with
DALE.

5.2.15.1.       SPSYNC (Spindle synchronization) (Optional)

The definition of this signal is vendor specific.

5.2.15.2.       CSEL (Cable select) (Optional)

The device is configured as either Device 0 or Device 1 depending upon the value
of CSEL:

*       If CSEL is negated then the device address is 0
*       If CSEL is asserted then the device address is 1

CSEL shall be maintained at a steady level for at least 31 seconds after
the negation of RESET-.

Implementor's Note:
Special cabling can be used by the system manufacturer to selectively ground
CSEL e.g.  CSEL of Device 0 is connected to the CSEL conductor in the cable, and
is grounded, thus allowing the device to recognize itself as Device 0.  CSEL of
Device 1 is not connected to CSEL because the conductor is removed, thus the
device can recognize itself as Device 1.

                    +------ CSEL Conductor --------------------------+
                    |                            |                 Open
                    |Ground                      |                   |
                 +------+                   +----------+        +----------+
                 | Host |                   | Device 0 |        | Device 1 |
                 +------+                   +----------+        +----------+

                    +------ CSEL Conductor --------------------------+
                    |                          Open                  |
                    |Ground                      |                   |
                 +------+                   +----------+        +----------+
                 | Host |                   | Device 1 |        | Device 0 |
                 +------+                   +----------+        +----------+

Figure 4 - Cable Select Example




6.      Interface Register Definitions and Descriptions

6.1.    Device Addressing Considerations

In traditional controller operation, only the selected controller receives
commands from the host following selection.  In this standard, the register
contents go to both devices (and their embedded controllers).  The host
discriminates between the two by using the DEV bit in the Device/Head register.

Data is transferred in parallel (16 bits) either to or from host memory to the
device's buffer under the direction of commands previously transferred from the
host.  The device performs all of the operations necessary to properly write
data to, or read data from, the media.  Data read from the media is stored in
the device's buffer pending transfer to the host memory and data is transferred
from the host memory to the device's buffer to be written to the media.

The devices using this interface shall be programmed by the host computer to
perform commands and return status to the host at command completion.  When two
devices are daisy chained on the interface, commands are written in parallel to
both devices, and for all except the Execute Diagnostics command, only the
selected device executes the command.  On an Execute Diagnostics command
addressed to Device 0, both devices shall execute the command, and Device 1
shall post its status to Device 0 via PDIAG-.

Devices are selected by the DEV bit in the Device/Head register (see clause
6.2.7).  When the DEV bit is equal to zero, Device 0 is selected.  When the DEV
bit is equal to one, Device 1 is selected.  When devices are daisy chained, one
shall be set as Device 0 and the other as Device 1.  When a single device is
attached to the interface it shall be set as Device 0.

6.2.    I/O register descriptions

Communication to or from the device is through an I/O Register that routes the
input or output data to or from registers addressed by the signals from the host
(CS0-, CS1-, DA2, DA1, DA0, DIOR- and DIOW-).

The Command Block Registers are used for sending commands to the device or
posting status from the device.  The Control Block Registers are used for device
control and to post alternate status.

Table 7 lists these registers and the addresses that select them.

+===============================-==========================================+
|         Addresses             |                 Functions                |
|-------------------------------+------------------------------------------|
| CS0- | CS1- | DA2 | DA1 | DA0 |    READ (DIOR-)     |   WRITE (DIOW-)    |
|------+------+-----+-----+-----+------------------------------------------|
|  N   |  N   |  x  |  x  |  x  | Data bus high imped | Not Used           |
|------+------+-----+-----+-----+------------------------------------------|
|                               |        Control block registers           |
|-------------------------------+------------------------------------------|
|  N   |  A   |  0  |  x  |  x  | Data bus high imped | Not Used           |
|  N   |  A   |  1  |  0  |  x  | Data bus high imped | Not Used           |
|  N   |  A   |  1  |  1  |  0  | ALTERNATE STATUS    | DEVICE CONTROL     |
|  N   |  A   |  1  |  1  |  1  | (Note 1)            | Not Used           |
|-------------------------------+------------------------------------------|
|                               |        Command block registers           |
|-------------------------------+------------------------------------------|
|  A   |  N   |  0  |  0  |  0  | Data                | Data               |
|  A   |  N   |  0  |  0  |  1  | Error               | Features           |
|  A   |  N   |  0  |  1  |  0  | Sector Count        | Sector Count       |
|  A   |  N   |  0  |  1  |  1  | Sector Number       | Sector Number      |
|  A   |  N   |  0  |  1  |  1  | * LBA bits  0- 7    | * LBA bits  0- 7   |
|  A   |  N   |  1  |  0  |  0  | Cylinder Low        | Cylinder Low       |
|  A   |  N   |  1  |  0  |  0  | * LBA bits  8-15    | * LBA bits  8-15   |
|  A   |  N   |  1  |  0  |  1  | Cylinder High       | Cylinder High      |
|  A   |  N   |  1  |  0  |  1  | * LBA bits 16-23    | * LBA bits 16-23   |
|  A   |  N   |  1  |  1  |  0  | Device/Head         | Device/Head        |
|  A   |  N   |  1  |  1  |  0  | * LBA bits 24-27    | * LBA bits 24-27   |
|  A   |  N   |  1  |  1  |  1  | Status              | Command            |
|-------------------------------+------------------------------------------|
|  A   |  A   |  x  |  x  |  x  | Invalid address     | Invalid address    |
|--------------------------------------------------------------------------|
|                       * Mapping of registers in LBA mode                 |
+==========================================================================+
Logic conventions are:  A = signal asserted, N = signal negated, x = don't care

Note 1:  This register is obsolete.  It is recommended that a device not respond
to a read of this address.  If a device does respond, it shall be sure not to
drive the DD7 signal to prevent possible conflict with floppy disk
implementations.

Table 7 - I/O Port Functions and Selection Addresses


6.2.1.  Alternate Status register

This register contains the same information as the Status register in the
command block.  The only difference being that reading this register does not
imply interrupt acknowledge or clear a pending interrupt.

+=======+=======+=======+=======+=======+=======+=======+=======+
|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
|-------+-------+-------+-------+-------+-------+-------+-------|
|  BSY  | DRDY  |  DF   |  DSC  |  DRQ  | CORR  |  IDX  |  ERR  |
+=======+=======+=======+=======+=======+=======+=======+=======+

See clause 6.2.12 for definitions of the bits in this register.

6.2.2.  Command register

This register contains the command code being sent to the device.  Command
execution begins immediately after this register is written.  The executable
commands, the command codes, and the necessary parameters for each command are
listed in table 10.

6.2.3.  Cylinder High register

In CHS Mode, this register contains the high order bits of the starting cylinder
address for any media access.  In LBA Mode, this register contains Bits 23-16 of
the LBA for any media access.

This register shall be updated to reflect the media address of the error when a
media access command is unsuccessfully completed.

Implementor's Note:  Prior to the development of this standard, this register
was updated at the end of every media access command to reflect the current
media address.

6.2.4.  Cylinder Low register

In CHS Mode, this register contains the low order bits of the starting cylinder
address for any media access.  In LBA Mode, this register contains Bits 15-8 of
the LBA for any media access.

This register shall be updated to reflect the media address of the error when a
media access command is unsuccessfully completed.

Implementor's Note:  Prior to the development of this standard, this register
was updated at the end of every media access command to reflect the current
media address.

6.2.5.  Data register

The data register is either 8-bits or 16-bits depending on the interface width
currently selected and/or the type of data being transferred by the current
command.

6.2.6.  Device Control register

The bits in this register are as follows:

+=======+=======+=======+=======+=======+=======+=======+=======+
|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
|-------+-------+-------+-------+-------+-------+-------+-------|
|   r   |   r   |   r   |   r   |   r   | SRST  |  nIEN |   0   |
+=======+=======+=======+=======+=======+=======+=======+=======+

-       Bits 7 through 3 are reserved.

*       SRST is the host software reset bit.  The device is held reset when this
bit is set.  If two devices are daisy chained on the interface, this bit
resets both simultaneously.

*       nIEN is the enable bit for the device interrupt to the host.  When
the nIEN bit is equal to zero, and the device is selected, INTRQ shall be
enabled through a tri-state buffer.  When the nIEN bit is equal to one, or
the device is not selected, the INTRQ signal shall be in a high impedance
state.

6.2.7.  Device/Head register

This register contains device addressing and sector addressing information.

+=======+=======+=======+=======+=======+=======+=======+=======+
|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
|-------+-------+-------+-------+-------+-------+-------+-------|
|   r   |   L   |   r   |  DEV  |  HS3  |  HS2  |  HS1  |  HS0  |
+=======+=======+=======+=======+=======+=======+=======+=======+

*       Bit 7 is reserved.
*       L is the sector address mode select.  When the L bit is equal to zero,
addressing is by CHS  mode.  When the L bit is equal to one, addressing is
by LBA mode.
*       Bit 5 is reserved.
*       DEV is the device address.  When the DEV bit is equal to zero, Device 0 is
selected.  When the DEV bit is equal to one, Device 1 is selected.
*       If the L bit is equal to zero (CHS Mode), the HS3 through HS0 bits contain
the head address of the CHS address.  The HS3 bit is the most significant
bit.  If the L bit is equal to one (LBA Mode), the HS3 through HS0 bits
contain bits 27 through 24 of the LBA. This field shall be updated to
reflect the media address of the error when a media access command is
unsuccessfully completed.

Implementor's Note:  Prior to the development of this standard, the head field
(the HS3 through HS0 bits) of this register was updated at the end of every
media access command to reflect the current media address.

6.2.8.  Error register

This register contains status from the last command executed by the device or a
Diagnostic Code.

At the completion of any command except EXECUTE DEVICE DIAGNOSTIC, the contents
of this register are valid when the ERR bit is equal to one in the Status
register.

Following a power on, a reset, or completion of an EXECUTE DEVICE DIAGNOSTIC
command, this register contains a diagnostic code (see table 11).

+=======+=======+=======+=======+=======+=======+=======+=======+
|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
|-------+-------+-------+-------+-------+-------+-------+-------|
|   r   |  UNC  |  MC   | IDNF  |  MCR  | ABRT  | TK0NF | AMNF  |
+=======+=======+=======+=======+=======+=======+=======+=======+

*       Bit 7 is reserved.
*       UNC (Uncorrectable Data Error) indicates an uncorrectable data error has
been encountered.
*       MC (Media Changed) is reserved for use by removable media devices and
indicates that new media is available to the operating system.  The MC bit
shall be cleared by either a hardware reset or a power on reset.
The first command following a media change shall be rejected with the MC
bit set in the error register and the ERR bit set in the status register.
The media changed state shall then be cleared and subsequent commands
accepted normally.
*       IDNF (ID Not Found) indicates the requested sector's ID field could not be
found.
*       ABRT (Aborted Command) indicates the requested command has been aborted
because the  command code is invalid or another device error has occurred.
*       MCR (Media Change Requested) is reserved for use by removable media
devices and indicates that a request for media removal has been detected
by the device.  When a request for media removal is detected, the MCR bit
shall be returned in the error register and the ERR bit set in the status
register for all subsequent DOOR LOCK commands.  The MCR bit shall be
cleared by a DOOR UNLOCK command, a MEDIA EJECT command or by a hard
reset.
*       TK0NF (Track 0 Not Found) indicates track 0 has not been found during a
RECALIBRATE command.
*       AMNF (Address Mark Not Found) indicates the data address mark has not been
found after finding the correct ID field.

6.2.9.  Features register

This register is command specific and may be used to enable and disable features
of the interface e.g.  by the SET FEATURES Command to enable and disable
caching.

This register may be ignored by some devices.

Some hosts, based on definitions prior to the completion of this standard, set
values in this register to designate a recommended Write Precompensation
Cylinder value.



6.2.10. Sector Count register

This register contains the number of sectors of data requested to be transferred
on a read or write operation between the host and the device.  If the value in
this register is zero, a count of 256 sectors is specified.

For media access commands, this register shall be zero at the completion of a
command if there is no error indication in the Status register.  For media
access commands that complete with an error indication in the Status register,
this register contains the number of sectors which need to be transferred in
order to complete the request.

The contents of this register may be redefined on some commands, e.g.
INITIALIZE DEVICE PARAMETERS or WRITE SAME commands.

6.2.11. Sector Number register

In CHS Mode, this register contains the starting sector number for any media
access.  In LBA Mode, this register contains Bits 7-0 of the LBA for any media
access.  This register is used by some non-media access commands to pass command
specific information from the host to the device, or from the device to the
host.

This register shall be updated to reflect the media address of the error when a
media access command is unsuccessfully completed.

Implementor's Note:  Prior to the development of this standard, this register
was updated at the end of every media access command to reflect the current
media address.



6.2.12. Status register

This register contains the device status.  The contents of this register are
updated to reflect the current state of the device and the progress of any
command being executed by the device.  When the BSY bit is equal to zero, the
other bits in this register are valid and the other Command Block register may
contain meaningful information.  When the BSY bit is equal to one, no other bits
in this register and all other Command Block registers are not valid.

NOTE:  Although host systems might be capable of generating read cycles shorter
than the 400 ns specified for status update following the last command or data
cycle, host implementations should wait at least 400 ns before reading the
status register to insure that the BSY bit is valid.

For devices that implement the Power Management features, the contents of the
Status register and all other Command Block registers are not valid while a
device is in the Sleep mode.

If the host reads this register when an interrupt is pending, the interrupt is
cleared.

+=======+=======+=======+=======+=======+=======+=======+=======+
|   7   |   6   |   5   |   4   |   3   |   2   |   1   |   0   |
|-------+-------+-------+-------+-------+-------+-------+-------|
|  BSY  | DRDY  |  DF   |  DSC  |  DRQ  | CORR  |  IDX  |  ERR  |
+=======+=======+=======+=======+=======+=======+=======+=======+

- BSY (Busy) is set whenever the device has control of the command Block
Registers.  When the BSY bit is equal to one, a write to a command block
register by the host shall be ignored by the device.

The device shall not change the state of the DRQ bit unless the BSY bit is
equal to one.  When the last block of a PIO data in command has been
transferred by the host, then the DRQ bit is cleared without the BSY bit
being set.

When the BSY bit equals zero, the device may only change the IDX, DRDY,
DF, DSC and CORR bits in the Status register and the Data register.  All
of the other command block registers and bits within the Status register
shall not be changed by the device.

Note:  The assertion of CORR by the device while the BSY bit is set to
zero might not be recognized by BIOS and drivers which sample status as
soon as the BSY bit is equal to zero.

The BSY bit shall be set by the device under the following circumstances:

a) within 400 nsec after either the negation of RESET- or the setting of
the SRST bit in the Device Control register.

b) within 400 nsec after the acceptance of a command if the DRQ bit is not
set.

c) between blocks of a data transfer during PIO data in commands if the
DRQ bit is not set.

d) after the transfer of a data block during PIO data out commands if the
DRQ bit is not set.

e) during the data transfer of DMA commands if the DRQ bit is not set.

The device shall not set the BSY bit at any other time.

When the BSY bit is set due to the negation of RESET- or the setting of
the SRST bit, the BSY bit shall remain set until the device has completed
processing of the reset condition.

When a command is accepted either the BSY bit shall be set, or if the BSY
bit is cleared, the DRQ bit shall be set, until command completion.

Implementor's Note:  There may be times when the BSY bit is set and then
cleared so quickly, that the host may not be able to detect that the BSY
bit had been set.

*       DRDY (Device Ready) is set to indicate that the device is capable of
accepting all command codes.  This bit shall be cleared at power on.
Devices that implement the power management features shall maintain the
DRDY bit equal to one when they are in the Idle or Standby power modes.
When the state of the DRDY bit changes, it shall not change again until
after the host reads the Status register.

When the DRDY bit is equal to zero, a device responds as follows:

a) the device shall accept and attempt to execute the EXECUTE DEVICE
DIAGNOSTIC and INITIALIZE DEVICE PARAMETERS commands.

b) the device should reject all other commands codes by setting the ABRT
bit in the Error register and setting the ERR bit in the Status register
before clearing the BSY bit to signal the command completion.  If a device
accepts commands other than EXECUTE DEVICE DIAGNOSTIC and INITIALIZE
DEVICE PARAMETERS during the time the DRDY bit is equal to zero, the
results are vendor specific.

*       DF (Device Fault) indicates a device fault error has been detected.  The
internal status or internal conditions that causes this error to be
indicated is vendor specific.

*       DSC (Device Seek Complete) indicates that the device heads are settled
over a track.  When an error occurs, this bit shall not be changed until
the Status  Register is read by the host, at which time the bit again
indicates the current Seek Complete status.

*       DRQ (Data Request) indicates that the device is ready to transfer a word
or byte of data between the host and the device.

*       CORR (Corrected Data) is used to indicate a correctable data error.  The
definition of what constitutes a correctable error is vendor specific.
This condition does not terminate a data transfer.

*       IDX (Index) is vendor specific.

*       ERR (Error) indicates that an error occurred during execution of the
previous command.  The bits in the Error register have additional
information regarding the cause of the error.  Once the device has set the
error bit, the device shall not change the contents of the following items
until a new command has been accepted, the SRST bit is set to one or
RESET- is asserted:
the ERR bit in the status register
Error register
Cylinder High register
Cylinder Low register
Sector Count register
Sector Number register
Device/Head register.

7.      General Operational Requirements

7.1.    Reset response

There are three types of reset in ATA.  The following is a suggested method of
classifying reset actions:

*       Power On Reset: the device executes a series of electrical circuitry
diagnostics, spins up the HDA, tests speed and other mechanical
parametrics, and sets default values.
*       Hardware Reset: the device executes a series of electrical circuitry
diagnostics, and resets to default values.
*       Software Reset: the device resets the interface circuitry according to
the Set Features requirement (See clause 8.24)

The power on reset, hardware reset and software reset protocols are defined in
clauses 9.1 and 9.2.


7.2.    Sector Addressing

All addressing of data sectors recorded on the device's media is by a logical
sector address.  The mapping of logical sector addresses to the actual physical
location of the data sector on the media is vendor specific.

An ATA device shall support at least one logical CHS translation mode known as
the default translation mode.  The device shall enter this translation mode
following a reset.  A device may support other logical translation modes and the
host may use the INITIALIZE DEVICE PARAMETERS command to select the default CHS
mode or any of the other supported CHS modes.  The default translation mode is
described in the Identify Device information.  The current translation mode may
also be described in the Identify Device information.

A CHS address is made up of three fields:  the sector address, the head number
and the cylinder number.  Sectors are numbered from 1 to the maximum value
allowed by the current CHS translation mode but can not exceed 255.  Heads are
numbered from 0 to the maximum value allowed by the current CHS translation mode
but can not exceed 15.  Cylinders are numbered from 0 to the maximum value
allowed by the current CHS translation mode but cannot exceed 65,535.

When the host selects a CHS translation mode using the INITIALIZE DEVICE
PARAMETERS command, the host requests the number of sectors per logical track
and the number of heads per logical cylinder.  The device then computes the
number of logical cylinders available in requested mode.

Sequential access to logical sectors shall be accomplished by treating the
sector number as the least significant portion of the logical sector address,
the head number as the middle portion of the logical sector address and the
cylinder number as the most significant portion of the logical sector address.

A device may support LBA addressing.  A device that supports LBA addressing
indicates this in the Identify Device information.  A host shall not attempt to
use LBA addressing unless the device indicates the mode is supported.

A device shall not change the addressing method and shall return status
information utilizing the addressing method specified for the command.

If a device supports LBA addressing mode, then the following shall be supported
by the device:

1) The host may select either the currently selected CHS translation addressing
or LBA addressing on a command-by-command basis by using the L bit in the
Device/Head register.

2) If LBA addressing is supported, then the device shall supported LBA
addressing for all media access commands, except for the FORMAT TRACK command.
Implementation of LBA addressing for the FORMAT TRACK command is vendor
specific.  The L bit of the Device/Head register shall be ignored for commands
that do not access the media.

3) Logical sectors on the device shall be linearly mapped with the first LBA
addressed sector (sector 0) being the same sector as the first logical CHS
addressed sector (cylinder 0, head 0, sector 1).  Irrespective of the logical
CHS translation mode currently in effect, the LBA address of a given logical
sector does not change.  The following is always true:

LBA = ( (cylinder * heads_per_cylinder + heads )
        * sectors_per_track ) + sector - 1

where heads_per_cylinder and sectors_per_track are the current translation mode
values.

7.3.    Power Management Feature Set

The Power Management Feature Set permits a host to modify the behavior of a
device in a manner which reduces the power required to operate.  The Power
Management Feature Set provides a set of commands and a timer that enable a
device to implement low power consumption modes.  A device that implements the
Power Management feature shall implement the following minimum set of functions:

1) A Standby timer
2) Idle command
3) Idle Immediate command
4) Sleep command
5) Standby command
6) Standby Immediate command

Additional vendor specific commands and functions are allowed.

7.3.1.  Power modes

The lowest power consumption when the device is powered on occurs in Sleep Mode.
When in Sleep Mode, the device requires a reset to be activated.  The time to
respond could be as long as 30 seconds.

In Standby Mode the device interface is capable of accepting commands, but as
the media may not immediately accessible, it could take the device as long as 30
seconds to respond.

In Idle Mode the device is capable of responding immediately to media access
requests.  A device in Idle Mode may take longer to complete the execution of a
command because it may have to activate some circuitry.

In Active mode the device is capable of responding immediately to media access
requests, and commands complete execution in the shortest possible time.  During
the execution of a media access command a device shall be in Active mode.

7.3.2.  Power Management Commands

The Check Power Mode command allows a host to determine if a device is currently
in, going to or leaving Standby mode.

The Idle and Idle Immediate commands move a device to Idle mode immediately from
the Active or Standby modes.  The Idle command also sets the Standby Timer count
and enables or disables the Standby Timer.

The Sleep command moves a device to Sleep mode.  The device's interface becomes
inactive at the completion of the Sleep command.  A reset is required to move a
device out of Sleep mode.  When a device exits Sleep mode it may enter Active,
Idle or Standby mode.  The mode selected by the device is based on the type of
reset received and on vendor specific implementation.

The Standby and Standby Immediate commands move a device to Standby mode
immediately from the Active or Idle modes.  The Standby command also sets the
Standby Timer count and enables or disables the Standby Timer.

7.3.3.  Standby timer

The Standby timer provides a method for the device to automatically enter
Standby mode from either Active or Idle mode following a host programmed period
of inactivity.  If the Standby timer is enabled and if the device is in the
Active or Idle mode, the device waits for the specified time period and if no
command is received, the device automatically enters the Standby mode.

If the Standby Timer is disabled, the device may not automatically enter Standby
mode.

7.3.4.  Idle mode transition

The transition to Idle mode is vendor specific, and may occur as a result of an
IDLE or IDLE IMMEDIATE command, or in vendor specific way.

7.3.5.  Status

In the Active, Idle and Standby modes, the device shall have DRDY bit of the
Status register set and, if BSY bit is not set, shall be ready to accept any
command.

In Sleep mode, the device's interface is not active.  A host shall not attempt
to read the device's status or issue commands to the device.

7.3.6.  Power Mode transitions

Figure 5 shows the minimum set of mode transitions that shall be implemented.

                         +========+
                         |        |-----------------------+
       +--------1--------| ACTIVE |-------3---------+     |
       | +------4------->|        |<------4-------+ |     |
       | |               +========+               | |     |
       V |                                        | V     5
   +=======+                                 +=========+  |
   |       |<----------------2---------------|         |  |
   |  IDLE |                                 | STANDBY |  |
   |       |-----------------3-------------->|         |  |
   +=======+                                 +=========+  |
        |                 +=======+               |       |
        |                 |       |               |       |
        +-------5-------->| SLEEP |<------5-------+       |
                          |       |<----------------------+
                          +=======+
                             |
      Resets ------6-----+   6
                         |   |
                         V   V
                     (see Path 6)

   Path 1: An Idle command, Idle Immediate command, or
           vendor specific implementation moves the device to Idle mode.
   Path 2: An Idle command or Idle Immediate command moves the
           device to Idle mode.
   Path 3: A Standby command, Standby Immediate or Standby timer
           expiration moves the device to Standby mode.
   Path 4: A Media access command moves the device to Active mode.
   Path 5: A Sleep command moves the device to Sleep mode.
   Path 6: A reset, either hardware or software, moves the
           device to Active, Idle or Standby as specified by
           the device vendor.

   Figure 5 - Power Management Modes




7.3.7.  Interface Capability For Power Modes

The optional power commands permit the host to modify the behavior of the device
in a manner which reduces the power required to operate.  These modes also
affect the physical interface as defined in the following table:

               +==========-=====-====-==================-=====+
               |   Mode   | BSY |DRDY| Interface active |Media|
               |----------+-----+----+------------------+-----|
               | Sleep    |  x  |  x |        No        |  I  |
               |          |     |    |                  |     |
               | Standby  |  0  |  1 |        Yes       |  I  |
               |          |     |    |                  |     |
               | Idle     |  0  |  1 |        Yes       |  A  |
               |          |     |    |                  |     |
               | Active   |  x  |  x |        Yes       |  A  |
               |----------------------------------------------|
               |   A = Active    I = Inactive                 |
               +==============================================+

Table 8 - Power Conditions

Ready is not a power condition.  A device may post ready at the interface even
though the media may not be accessible.

Also see specific power-related commands.


7.4.    Removable media mode transitions

Figure 6 shows the minimum set of mode transitions that shall be implemented by
removable media devices which contain a media change request mechanism (button)
and support the DOOR LOCK and DOOR UNLOCK commands, and the MC and MCR bits in
the Error register.

     +=============+
     |   State A   |
     | Ready       |
     | Unlocked    |
 +-->| Door closed |
 |   | Button off  |
 |   | MC active   |
 |   +=============+
 |    1.ANY COMMAND
 |          |
 |      MC status
 |          |
 |          V
 |   +=============+                  +==============+
 |   |   State B   |                  |    State C   |
 |   | Ready       |--3.DOOR LOCK---->| Ready        |-5.DOOR LOCK-+
 |   | Unlocked    |                  | Locked       |             |
 |   | Door closed |                  | Door closed  |<--- Good ---+
 |   | Button off  |<--4.DOOR UNLOCK--| Button off   |    status
 |   | MC cleared  |                  |              |
 |   +=============+                  +==============+
 |          |                                |
 |      2.Media change request       6.Media change request
 10.Door   (Button pushed)              (Button pushed)
 closed     |                                |
 |          V                                V
 |   +=============+                  +==============+
 +---|   State E   |<--8.DOOR UNLOCK--|    State D   |
     | Not Ready   |                  | Ready        |
     | Unlocked    |--9.DOOR LOCK--+  | Locked       |-7.DOOR LOCK-+
     | Door open   |               |  | Door closed  |             |
     | Button off  |<---- ABRT ----+  | Button pushed|<--- MCR ----+
     +=============+     status       +==============+    status

Figure 6 - Removable Modes




State A: Following a media change, the device is ready, the media is not locked,
the door is closed, the media change request button is not active and a
media change has been detected.
Path 1:  The first command following a media change shall be rejected with the
MC bit set in the Error register.  The device shall then be moved to
state B and the MC condition shall be cleared.

State B: In normal operation, the device is ready, the media is not locked, the
door is closed, the media change request button is not active and the
MC bit is off.
Path 2:  Activating the media change request button shall cause the device to
complete any pending operations, spin down the device, if needed, and
move to state E, allowing media removal.
Path 3:  A DOOR LOCK command shall lock the media and move the device to state
C.

State C: In normal operation, the device is ready, the media is locked, the door
is closed and the media change request button is not active.
Path 4:  A DOOR UNLOCK command shall unlock the media and move the device to
state B.
Path 5:  A DOOR LOCK command shall return good status.
Path 6:  Pushing the media change button shall move the device to state D.

State D: The device is ready, the media is locked, the door is closed and the
media change button is active.
Path 7:  A DOOR LOCK command shall return MCR status.
Path 8:  A DOOR UNLOCK command shall move the device to state E, allowing media
removal.

State E: The device is not ready, the media is not locked, the door is open and
the media change button is not active.
Path 9:  A DOOR LOCK command shall return an ABRT error status.
Path 10: Closing the door shall move the device to state A (ready) and shall set
the MC bit.

Figure 6 - Removable Modes (cont.)



7.5.    Status and Error posting

The status and errors that are valid for each command are defined in table 9.
It is not a requirement that all valid conditions be implemented.  See clauses
6.2.8 and 6.2.12 for the definition of the Error register and Status register
bits.

+=============================-=================-============================+
|                             | Status register |       Error register       |
|-----------------------------+-----------------+----------------------------|
|                             |DRDY|DF |CORR|ERR|BBK|UNC|IDNF|ABRT|TK0NF|AMNF|
|-----------------------------+----+---+----+---+---+---+----+----+-----+----|
| ACKNOWLEDGE MEDIA CHANGE    |  V | V |    | V |   |   |    |  V |     |    |
| BOOT - POST-BOOT            |  V | V |    | V |   |   |    |  V |     |    |
| BOOT - PRE-BOOT             |  V | V |    | V |   |   |    |  V |     |    |
| CHECK POWER MODE            |  V | V |    | V |   |   |    |  V |     |    |
| DOOR LOCK                   |  V | V |    | V |   |   |    |  V |     |    |
| DOOR UNLOCK                 |  V | V |    | V |   |   |    |  V |     |    |
| DOWNLOAD MICROCODE          |  V | V |    | V |   |   |    |  V |     |    |
|                             |    |   |    |   |----------------------------|
| EXECUTE DEVICE DIAGNOSTIC   |  V | V |    | V |         See 8.8            |
|                             |    |   |    |   |----------------------------|
| FORMAT TRACK                |  V | V |    | V | V | V |  V |  V |  V  |  V |
| IDENTIFY DEVICE             |  V | V |    | V |   |   |    |  V |     |    |
| IDLE                        |  V | V |    | V |   |   |    |  V |     |    |
| IDLE IMMEDIATE              |  V | V |    | V |   |   |    |  V |     |    |
| INITIALIZE DEVICE PARAMETERS|  V | V |    |   |   |   |    |    |     |    |
| MEDIA EJECT                 |  V | V |    | V |   |   |    |  V |     |    |
| NOP                         |  V | V |    | V |   |   |    |  V |     |    |
| READ BUFFER                 |  V | V |    | V |   |   |    |  V |     |    |
| READ DMA (w/ retry)         |  V | V |  V | V | V | V |  V |  V |     |  V |
| READ DMA (w/o retry)        |  V | V |  V | V | V | V |  V |  V |     |  V |
| READ LONG (w/ retry)        |  V | V |    | V | V |   |  V |  V |     |  V |
| READ LONG (w/o retry)       |  V | V |    | V | V |   |  V |  V |     |  V |
| READ MULTIPLE               |  V | V |  V | V | V | V |  V |  V |     |  V |
| READ SECTOR(S) (w/ retry)   |  V | V |  V | V | V | V |  V |  V |     |  V |
| READ SECTOR(S) (w/o retry)  |  V | V |  V | V | V | V |  V |  V |     |  V |
| READ VERIFY SECTOR(S)       |    |   |    |   |   |   |    |    |     |    |
|      (w/ retry)             |  V | V |  V | V | V | V |  V |  V |     |  V |
| READ VERIFY SECTOR(S) )     |    |   |    |   |   |   |    |    |     |    |
|      (w/o retry)            |  V | V |  V | V | V | V |  V |  V |     |  V |
| RECALIBRATE                 |  V | V |    | V |   |   |    |  V |  V  |    |
| SEEK                        |  V | V |    | V |   |   |  V |  V |     |    |
| SET FEATURES                |  V | V |    | V |   |   |    |  V |     |    |
| SET MULTIPLE MODE           |  V | V |    | V |   |   |    |  V |     |    |
| SLEEP                       |  V | V |    | V |   |   |    |  V |     |    |
| STANDBY                     |  V | V |    | V |   |   |    |  V |     |    |
| STANDBY IMMEDIATE           |  V | V |    | V |   |   |    |  V |     |    |
| WRITE BUFFER                |  V | V |    | V |   |   |    |  V |     |    |
| WRITE DMA (w/ retry)        |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE DMA (w/0 retry)       |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE LONG (w/ retry)       |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE LONG (w/o retry)      |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE MULTIPLE              |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE SAME                  |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE SECTOR(S) (w/ retry)  |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE SECTOR(S) (w/o retry) |  V | V |    | V | V |   |  V |  V |     |    |
| WRITE VERIFY                |  V | V | V  | V | V | V |  V |  V |     | V  |
|-----------------------------+----+---+----+---+---+---+----+----+-----+----|
| Invalid command code        |  V | V |    | V |   |   |    |  V |     |    |
|----------------------------------------------------------------------------|
| V = valid on this command                                                  |
+============================================================================+

Table 9 - Status and Error Usage


8.Command Descriptions

Commands are issued to the device by loading the pertinent registers in the
command block with the needed parameters, and then writing the command code to
the Command register.

Upon receipt of a command, the device sets the BSY bit or the DRQ bit within 400
nsec.  Following the setting of BSY bit equal to one or BSY bit equal to zero
and DRQ bit equal to one, the status presented by the device depends on the type
of command:  PIO data in, PIO data out, non-data transfer or DMA.  See the
individual command descriptions and Section 9 for the protocol followed by each
command and command type.

Note:  Some older host implementations may require the BSY bit being set to zero
and the DRQ bit equal to one in the Status register within 700 nsec of receiving
some PIO data out commands.

Note:  For the power mode related commands, it is recommended that the host
utilize E0h through E3h, E5h and E6h command values.  While command values 94h
through 99h command values are valid, they should be considered obsolete and may
be removed in future versions of this standard.

In table 10, the "proto" column codes represent the command protocol used:

  DM - A DMA command.
  ND - A non data command.
  PI - A PIO data in command.
  PO - A PIO data out command.
  VS - A Vendor specific command.

In table 10, the "typ" column codes represent the command type:

  O - Optional_the implementation of this command is optional.
  M - Mandatory_all ATA devices shall implement this command.
  R - Reserved for use in future ATA standards.
  V - Vendor specific implementation.


+=====-======================================-Command-=====Parameters Used====+
|proto|                                  |typ| code  | FR | SC | SN | CY | DH |
|-----+--------------------------------------+-------+----+----+----+----+----|
|  VS | ACKNOWLEDGE MEDIA CHANGE         | O |  DBh  |    |    |    |    |  D |
|  VS | BOOT - POST-BOOT                 | O |  DCh  |    |    |    |    |  D |
|  VS | BOOT - PRE-BOOT                  | O |  DDh  |    |    |    |    |  D |
|  ND | CHECK POWER MODE                 | O |98h E5h|    |  y |    |    |  D |
|  VS | DOOR LOCK                        | O |  DEh  |    |    |    |    |  D |
|  VS | DOOR UNLOCK                      | O |  DFh  |    |    |    |    |  D |
|  PO | DOWNLOAD MICROCODE               | O |  92h  |  y |  y |  y |  y |  D |
|  ND | EXECUTE DEVICE DIAGNOSTIC        | M |  90h  |    |    |    |    |  D*|
|  VS | FORMAT TRACK                     | V |  50h  |    |    |    |    |  d |
|  PI | IDENTIFY DEVICE                  | M |  ECh  |    |    |    |    |  D |
|  ND | IDLE                             | O |97h E3h|    |  y |    |    |  D |
|  ND | IDLE IMMEDIATE                   | O |95h E1h|    |    |    |    |  D |
|  ND | INITIALIZE DEVICE PARAMETERS     | M |  91h  |    |  y |    |    |  y |
|  ND | MEDIA EJECT                      | O |  EDh  |    |    |    |    |  D |
|  ND | NOP                              | O |  00h  |    |    |    |    |  y |
|  PI | READ BUFFER                      | O |  E4h  |    |    |    |    |  D |
|  DM | READ DMA (w/retry)               | O |  C8h  |    |  y |  y |  y |  y |
|  DM | READ DMA (w/o retry)             | O |  C9h  |    |  y |  y |  y |  y |
|  PI | READ LONG (w/retry)              | O |  22h  |    |  y |  y |  y |  y |
|  PI | READ LONG (w/o retry)            | O |  23h  |    |  y |  y |  y |  y |
|  PI | READ MULTIPLE                    | O |  C4h  |    |  y |  y |  y |  y |
|  PI | READ SECTOR(S) (w/retry)         | M |  20h  |    |  y |  y |  y |  y |
|  PI | READ SECTOR(S) (w/o retry)       | M |  21h  |    |  y |  y |  y |  y |
|  ND | READ VERIFY SECTOR(S) (w/retry)  | M |  40h  |    |  y |  y |  y |  y |
|  ND | READ VERIFY SECTOR(S) (w/o retry)| M |  41h  |    |  y |  y |  y |  y |
|  ND | RECALIBRATE                      | O |  1xh  |    |    |    |    |  D |
|  ND | SEEK                             | M |  7xh  |    |    |  y |  y |  y |
|  ND | SET FEATURES                     | O |  EFh  |  y |    |    |    |  D |
|  ND | SET MULTIPLE MODE                | O |  C6h  |    |  y |    |    |  D |
|  ND | SLEEP                            | O |99h E6h|    |    |    |    |  D |
|  ND | STANDBY                          | O |96h E2h|    |  y |    |    |  D |
|  ND | STANDBY IMMEDIATE                | O |94h E0h|    |    |    |    |  D |
|  PO | WRITE BUFFER                     | O |  E8h  |    |    |    |    |  D |
|  DM | WRITE DMA (w/retry)              | O |  CAh  |    |  y |  y |  y |  y |
|  DM | WRITE DMA (w/o retry)            | O |  CBh  |    |  y |  y |  y |  y |
|  PO | WRITE LONG (w/retry)             | O |  32h  |  * |  y |  y |  y |  y |
|  PO | WRITE LONG (w/o retry)           | O |  33h  |  * |  y |  y |  y |  y |
|  PO | WRITE MULTIPLE                   | O |  C5h  |  * |  y |  y |  y |  y |
|  PO | WRITE SAME                       | O |  E9h  |  y |  y |  y |  y |  y |
|  PO | WRITE SECTOR(S) (w/retry)        | M |  30h  |  * |  y |  y |  y |  y |
|  PO | WRITE SECTOR(S) (w/o retry)      | M |  31h  |  * |  y |  y |  y |  y |
|  PO | WRITE VERIFY                     | O |  3Ch  |  * |  y |  y |  y |  y |
|  VS | Vendor specific                  | V |  9Ah  |    |    |    |    |    |
|  VS | Vendor specific                  | V |C0h-C3h|    |    |    |    |    |
|  VS | Vendor specific                  | V |  8xh  |    |    |    |    |    |
|  VS | Vendor specific                  | V |F0h-FFh|    |    |    |    |    |
|  -- | Reserved: all remaining codes    | R |       |    |    |    |    |    |
|-----+-----------------------------------------------------------------------|
|     | CY = Cylinder registers         SC = Sector Count register            |
|     | DH = Device/Head register       SN = Sector Number register           |
|     | FR = Features register (see command descriptions for use)             |
|     | y - the register contains a valid parameter for this command.         |
|     |     For the Device/Head register, y means both the device and         |
|     |     head parameters are used.                                         |
|     | D - only the device parameter is valid and not the head parameter.    |
|     | d - the device parameter is valid, the usage of the head parameter    |
|     |     is vendor specific.                                               |
|     | D* - Addressed to device 0 but both devices execute it.               |
|     | * - Maintained for compatibility (see 6.2.9)                          |
+=============================================================================+
Table 10 - Command Codes and Parameters



Each command description in the following sections contain the following
subsections:

OPCODE - Indicates the command code for this command.

TYPE - Indicates if the command is mandatory, optional or vendor specific and,
if the command is a member of one or more feature sets, which feature sets it
belongs to.

PROTOCOL - Indicates which protocol is used by the command.

INPUTS - Describes the Command Block register data that the host shall supply.

NORMAL OUTPUTS - Describes the Command Block register data that shall be
returned by the device at the end of a command.  The Status register shall
always be valid and, if the ERR bit in the Status register is set to one, then
the Error register shall be valid.

ERROR OUTPUTS - Describes the Command Block register data that shall be returned
by the device at the end of a command which completes with an unrecoverable
error.

PREREQUISITES - Any prerequisite commands or conditions that shall be met before
the command can be issued.

DESCRIPTION - The description of the command function(s).



8.1.ACKNOWLEDGE MEDIA CHANGE (removable)

OPCODE - DBh

TYPE - Optional.

PROTOCOL - Vendor specific.

INPUTS - Vendor specific.

NORMAL OUTPUTS - Vendor specific.

ERROR OUTPUTS - Vendor specific or if the device does not support this command,
the device shall return a Command Abort error.

PREREQUISITES - Vendor specific.

DESCRIPTION - This command is reserved for use by removable media devices.  The
implementation of this command is vendor specific.



8.2.BOOT - POST-BOOT (removable)

OPCODE - DCh

TYPE - Optional.

PROTOCOL - Vendor specific.

INPUTS - Vendor specific.

NORMAL OUTPUTS - Vendor specific.

ERROR OUTPUTS - Vendor specific or if the device does not support this command,
the device shall return a Command Abort error.

PREREQUISITES - Vendor specific.

DESCRIPTION - This command is reserved for use by removable media devices.  The
implementation of this command is vendor specific.



8.3.BOOT - PRE-BOOT (removable)

OPCODE - DDh

TYPE - Optional.

PROTOCOL - Vendor specific.

INPUTS - Vendor specific.

NORMAL OUTPUTS - Vendor specific.

ERROR OUTPUTS - Vendor specific or if the device does not support this command,
the device shall return a Command Abort error.

PREREQUISITES - Vendor specific.

DESCRIPTION - This command is reserved for use by removable media devices.  The
implementation of this command is vendor specific.



8.4.CHECK POWER MODE

OPCODE - 98h or E5h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS - None.

NORMAL OUTPUTS - The Sector Count register is set to 0 (00h) if the device is
going to, in or leaving Standby mode.  The Sector Count register is set to 255
(FFh) if the device is in Active or Idle mode.

ERROR OUTPUTS - Aborted Command if the device does not support the Power
Management command set.

PREREQUISITES - None.

DESCRIPTION - If the device is in, going to, or recovering from the Standby Mode
the device shall set the BSY bit, set the Sector Count register to 0 (00h),
clear the BSY bit, and assert INTRQ.

If the device is in Active or Idle Mode, the device shall set the BSY bit, set
the Sector Count register to 255 (FFh), clear the BSY bit, and assert INTRQ.



8.5.DOOR LOCK (removable)

OPCODE - DEh

TYPE - Optional

PROTOCOL - Non-data command.

INPUTS - None.

NORMAL OUTPUTS - None.

ERROR OUTPUTS -  If the device is not ready or is not capable of locking the
media, the ABRT bit in the Error register and the ERR bit in the Status register
shall be returned.

If the device is already locked and the media change request button is active,
then a Media Change Requested status shall be returned by setting the MCR bit in
the Error register and the ERR bit in the Status register.

PREREQUISITES - None.

DESCRIPTION - This command either locks the device or media, or provides the
status of the media change request button.

If the device is not locked, the device shall be set to the locked state and
good status returned.

If the device is locked, the status returned shall indicate the state of the
media change request button.  Good status shall be returned while the media
change request button is not active, and the MCR bit in the Error register and
the ERR bit in the Status register shall be returned when the media change
request button is active.

When a device is in a DOOR LOCKED state, the device shall not respond to the
media change request button, except by setting the MCR status, until the DOOR
LOCKED condition is cleared.  A DOOR LOCK condition shall be cleared by a DOOR
UNLOCK or MEDIA EJECT command, or by a hardware device reset.




8.6.DOOR UNLOCK (removable)

OPCODE - DFh

TYPE - Optional

PROTOCOL - Non-data command.

INPUTS - None.

NORMAL OUTPUTS - None.

ERROR OUTPUTS -  If the device does not support this command or is not ready,
then the ABRT bit shall be returned in the Error register and the ERR bit shall
be returned in the Status register.

PREREQUISITES - None.

DESCRIPTION - This command shall unlock the device, if it is locked, and shall
allow the device to respond to the media change request button.



8.7.DOWNLOAD MICROCODE

OPCODE - 92h

TYPE - Optional.

PROTOCOL - PIO data out.

INPUTS - The head bits of the Device/Head register shall always be set to zero.
The Cylinder High and Low registers shall be set to zero.  The Sector Number and
Sector Count registers are used together as a 16-bit sector count value.  The
Feature register specifies the subcommand code.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the device does not support this command or
did not accept the microcode data.

PREREQUISITES - None.

DESCRIPTION - This command enables the host to alter the device's microcode.
The data transferred using the DOWNLOAD MICROCODE command is vendor specific.

All transfers shall be an integer multiple of the sector size.  The size of the
data transfer is determined by the contents of the Sector Number Register and
the Sector Count register.  The Sector Number Register shall be used to extend
the Sector Count register, to create a sixteen bit sector count value.  The
Sector Number Register shall be the most significant eight bits and the Sector
Count register shall be the least significant eight bits.  A value of zero in
both the Sector Number Register and the Sector Count register shall indicate no
data is to be transferred.  This allows transfer sizes from 0 bytes to 33 553
920 bytes, in 512 byte increments.
The Features register shall be used to determine the effect of the DOWNLOAD
MICROCODE command.  The values for the Feature Register are:

  01H - download is for immediate, temporary use
  07H - save downloaded code for immediate and future use

All other values are reserved.


8.8.EXECUTE DEVICE DIAGNOSTIC

OPCODE - 90h

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - None, except that the device selection bit in the Device/Head register
is ignored.

NORMAL OUTPUTS - The diagnostic code written into the Error register is an 8-bit
code as shown in table 11, and not as defined in clause 6.2.8.

+=========-==================================+
|  Code   | Description                      |
|---------+----------------------------------|
| 01h     | Device 0 passed                  |
|         | Device 1 passed or not present   |
|---------+----------------------------------|
| 00h,    | Device 0 failed                  |
| 02h-7Fh | Device 1 passed or not present   |
|---------+----------------------------------|
| 81h     | Device 1 failed, Device 0 passed |
|---------+----------------------------------|
| 80h,    | Device 1 failed, Device 0 failed |
| 82h-FFh |                                  |
+============================================+
Table 11 - Diagnostic Codes

The meaning of values other than 01h and 81h are vendor specific and
should be considered a diagnostic failed condition.

ERROR OUTPUTS - None.  All error information is returned as a diagnostic code in
the Error register.

PREREQUISITES - None.

DESCRIPTION - This command shall perform the internal diagnostic tests
implemented by the device.  See also clauses 6.2.8 and 6.2.12.  The DEV bit in
the Drive/Head register is ignored.  Both devices, if present, shall execute
this command.

Device 0 performs the following operations for this command:

a)      Device 0 sets the BSY bit within 400 nsec after the EXECUTE DEVICE
DIAGNOSTIC command is received.

b)      Device 0 performs diagnostics.

c)      Device 0 resets the Command Block registers to the following:

        CYLINDER LOW    = 00h           CYLINDER HIGH   = 00h
        SECTOR COUNT    = 01h           DEVICE/HEAD     = 00h
        SECTOR NUMBER   = 01h

d)      Device 0 posts diagnostic results to bits 6-0 of the Error Register.

e)      If Device 0 detected that Device 1 is present during the most recent power
on or hardware reset sequence, then Device 0 waits up to 6 seconds from
the time that the EXECUTE DEVICE DIAGNOSTIC command was received for
Device 1 to assert PDIAG-.  If PDIAG- is asserted within 6 seconds, Device
0 sets bit 7 to zero in the Error Register, else Device 0 sets bit 7 equal
to 1 in the Error Register.

        If device 1 was not detected during the most recent power up or hardware
reset sequence, then Device 0 sets bit 7 to zero in the Error register.

f)      Device 0 clears the BSY bit when ready to accept commands that do not
require the DRDY bit to be equal to 1.

NOTE: Device 0 shall clear the BSY bit within 6 seconds from the time that the
EXECUTE DEVICE DIAGNOSTIC command was received.

g)      Device 0 sets the DRDY bit when ready to accept any command.

NOTE: Steps f) and g) may occur at the same time.  While no maximum time is
specified for the DRDY bit to be set to one to occur, a host is advised to allow
up to 2 minutes for the DRDY bit to be set to one.  See Figure 7.

Device 1 performs the following operations for this command:

a)      Device 1 sets the BSY bit within 400 nsec after the EXECUTE DEVICE
DIAGNOSTIC command is received.

b)      Device 1 negates PDIAG- within 1 msec after the command is received.

c)      Device 1 performs diagnostics.

d)      Device 1 resets the Command Block registers to the following:

        CYLINDER LOW    = 00h           CYLINDER HIGH   = 00h
        SECTOR COUNT    = 01h           DEVICE/HEAD     = 00h
        SECTOR NUMBER   = 01h

e)      Device 1 sets bit 7 of the Error register to zero and posts its diagnostic
results to bits 6 through 0 of Error register.

f)      Device 1 clears the BSY bit when ready to accept commands that do not
require the DRDY bit to be equal to one.

g)      If Device 1 passed its diagnostics without error in step c), Device 1
asserts PDIAG-.  If the diagnostics failed, Device 1 does not assert
PDIAG- and continues to the next step.

NOTE:  Device 1 shall clear the BSY bit and assert PDIAG- within 5 seconds of
the time that the EXECUTE DEVICE DIAGNOSTIC command is received.

h)      Device 1 sets the DRDY bit when ready to accept any command.

NOTE:  Steps f), g) and h) may occur at the same time.  While no maximum time is
specified for the DRDY bit to set to one, a host is advised to allow up to 2
minutes for the DRDY bit to be equal to one.  See Figure 7.
            __________________
   BSY  ___/                  \______________________________
           |                  |                   ___________
   DRDY _________________________________________/
           |<---------------->|<---------------->|
             Max for device 0    Minimum time is
              is  6 seconds.     0 seconds.
             Max for device 1    No maximum time
              is  5 seconds.     is specified.
Figure 7 - BSY and DRDY timing for Diagnostic command



8.9.FORMAT TRACK

OPCODE - 50h

TYPE - Vendor specific.

PROTOCOL - Vendor specific.

INPUTS - Vendor specific.

NORMAL OUTPUTS - Vendor specific.

ERROR OUTPUTS - Aborted Command if the device does not support this command.
All other errors are vendor specific.

PREREQUISITES - Vendor specific.

DESCRIPTION - The implementation of the FORMAT TRACK command is vendor specific.
It is recommend that system implementations not utilize this command.



8.10.IDENTIFY DEVICE

OPCODE - ECh

TYPE - Mandatory

PROTOCOL - PIO data in.

INPUTS - None.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - None.

PREREQUISITES - None.

DESCRIPTION - The IDENTIFY DEVICE command enables the host to receive parameter
information from the device.

Some devices may have to read the media in order to complete this command.

When the command is issued, the device sets the BSY bit, prepares to transfer
the 256 words of device identification data to the host, sets the DRQ bit,
clears the BSY bit, and generates an interrupt.  The host can then transfer the
data by reading the Data register.  The parameter words in the buffer have the
arrangement and meanings defined in Table 12.  All reserved bits or words shall
be zero.

The F/V column indicates if the word or part of a word has fixed (F) contents
that do not change, variable (V) contents that may change depending on the
device state or the commands executed by the device, X for words with vendor
specific data which may be fixed or variable, and R for reserved words which
shall be zero. For removable media devices, the value of fields indicated as
fixed (F) may change when media is removed or changed.

Some parameters are defined as a group of bits.  A word which is defined as a
set of bits is transmitted with indicated bits on the respective data bus bit
(e.g., bit 15 appears on DD15).

Some parameters are defined as a sixteen bit value.  A word which is defined as
a sixteen bit value places the most significant bit of the value on bit DD15 and
the least significant bit on bit DD0.

Some parameters are defined as 32 bit values (e.g., words 57 and 58).  Such
fields are transferred using two word transfers.  The device shall first
transfer the least significant bits, bits 15 through 0 of the value, on bits
DD15 through DD0 respectively.  After the least significant bits have been
transferred, the most significant bits, bits 31 through 16 of the value, shall
be transferred on DD15 through DD0 respectively.

Some parameters are defined as a string of ASCII characters. For the string
"Copyright", the character `C' is the first byte, `o' is the 2nd byte, etc.
When such fields are transferred, the order of transmission is:

  the 1st character (`C') is on bits DD15 through DD8 of the first word
  the 2nd character (`o') is on bits DD7 through DD0 of the first word
  the 3rd character (`p') is on bits DD15 through DD8 of the second word
  the 4th character (`y') is on bits DD7 through DD0 of the second word
  etc.


+=======+===+==============================================================+
|  Word |F/V|                                                              |
|-------+---+--------------------------------------------------------------|
|    0  |   | General configuration bit-significant information:           |
|       | F |   15  0   reserved for non-magnetic devices                  |
|       | F |   14  Vendor specific (obsolete)                             |
|       | F |   13  Vendor specific (obsolete)                             |
|       | F |   12  Vendor specific (obsolete)                             |
|       | F |   11  Vendor specific (obsolete)                             |
|       | F |   10  Vendor specific (obsolete)                             |
|       | F |    9  Vendor specific (obsolete)                             |
|       | F |    8  Vendor specific (obsolete)                             |
|       | F |    7  1=removable media device                               |
|       | F |    6  1=not removable controller and/or device              |
|       | F |    5  Vendor specific (obsolete)                             |
|       | F |    4  Vendor specific (obsolete)                             |
|       | F |    3  Vendor specific (obsolete)                             |
|       | F |    2  Vendor specific (obsolete)                             |
|       | F |    1  Vendor specific (obsolete)                             |
|       | F |    0  Reserved                                               |
|    1  | F | Number of logical cylinders                                  |
|    2  | R | Reserved                                                     |
|    3  | F | Number of logical heads                                      |
|    4  | X | Vendor specific (obsolete)                                   |
|    5  | X | Vendor specific (obsolete)                                   |
|    6  | F | Number of logical sectors per logical track                  |
|  7-9  | X | Vendor specific                                              |
| 10-19 | F | Serial number                                                |
|   20  | X | Vendor specific (obsolete)                                   |
|   21  | X | Vendor specific (obsolete)                                   |
|   22  | F | # of vendor specific bytes avail on READ/WRITE LONG cmds     |
| 23-26 | F | Firmware revision (8 ASCII characters)                       |
| 27-46 | F | Model number (40 ASCII characters)                           |
|   47  | X | 15-8  Vendor specific                                        |
|       | F |  7-0  00h = READ/WRITE MULTIPLE commands not implemented     |
|       | F |       01h-FFh = Maximum number of sectors that can be        |
|       |   |             transferred per interrupt on READ MULTIPLE       |
|       |   |             and WRITE MULTIPLE commands                      |
|   48  | R | Reserved                                                     |
|   49  |   | Capabilities                                                 |
|       | R | 15-14  Reserved                                              |
|       | F |    13  1=Standby timer values as specified in this standard  |
|       |   |        are supported                                         |
|       |   |        0=Standby timer values are vendor specific            |
|       | R |    12  Reserved (for advanced PIO mode support)              |
|       | F |    11  1=IORDY supported                                     |
|       | F |        0=IORDY may be supported                              |
|       | F |    10  1=IORDY can be disabled                               |
|       | F |     9  1=LBA supported                                       |
|       | F |     8  1=DMA supported                                       |
|       | X |  7- 0  Vendor specific                                       |
|   50  | R | Reserved                                                     |
|   51  | F | 15-8  PIO data transfer cycle timing mode                    |
|       | X |  7-0  Vendor specific                                        |
|   52  | F | 15-8  DMA data transfer cycle timing mode                    |
|       | X |  7-0  Vendor specific                                        |
|-------+---+--------------------------------------------------------------|
Table 12 - Identify Device Information (Part 1 of 2)



+=======+===+==============================================================+
|  Word |F/V|                                                              |
|-------+---+--------------------------------------------------------------|
|   53  | R | 15-2  Reserved                                               |
|       | F |    1  1=the fields reported in words 64-70 are valid         |
|       | F |       0=the fields reported in words 64-70 are not valid     |
|       | V |    0  1=the fields reported in words 54-58 are valid         |
|       | V |       0=the fields reported in words 54-58 may be valid      |
|   54  | V | Number of current logical cylinders                          |
|   55  | V | Number of current logical heads                              |
|   56  | V | Number of current logical sectors per track                  |
| 57-58 | V | Current capacity in sectors                                  |
|   59  | R | 15-9  Reserved                                               |
|       | V |    8  1 = Multiple sector setting is valid                   |
|       | V |  7-0  xxh = Current setting for number of sectors that can be|
|       |   |             transferred per interrupt on R/W multiple command|
| 60-61 | F | Total number of user addressable sectors (LBA mode only)     |
|   62  | V | 15-8  Single word DMA transfer mode active                   |
|       | F |  7-0  Single word DMA transfer modes supported               |
|   63  | V | 15-8  Multiword DMA transfer mode active                     |
|       | F |  7-0  Multiword DMA transfer modes supported                 |
|   64  | R | 15-8  Reserved                                               |
|       | F |  7-0  Advanced PIO Transfer Modes Supported                  |
|   65  |   | Minimum Multiword DMA Transfer Cycle Time Per Word           |
|       | F | 15-0  Cycle time in nanoseconds                              |
|   66  |   | Manufacturer's Recommended Multiword DMA Transfer Cycle Time |
|       | F | 15-0  Cycle time in nanoseconds                              |
|   67  |   | Minimum PIO Transfer Cycle Time Without Flow Control         |
|       | F | 15-0  Cycle Time in nanoseconds                              |
|   68  |   | Minimum PIO Transfer Cycle Time With IORDY Flow Control      |
|       | F | 15-0  Cycle Time in nanoseconds                              |
| 69-70 | R | Reserved (for advanced PIO mode support)                     |
| 71-127| R | Reserved                                                     |
|128-159| X | Vendor specific                                              |
|160-255| R | Reserved                                                     |
+=======+===+==============================================================+
Table 12 - Identify Device Information (Part 2 of 2)

If the device has been configured for eight bit transfers, then each word as
defined in this table is transferred as described in clause 3.2.5.

8.10.1.Word 0: General configuration

Devices that conform to this standard shall set bit 15 to zero.

8.10.2.Word 1: Number of cylinders

The number of user-addressable logical cylinders in the default translation
mode.

8.10.3.Word 2: Reserved.

8.10.4.Word 3: Number of logical heads

The number of user-addressable logical heads per logical cylinder in the default
translation mode.

8.10.5.Word 4: Vendor specific data.

8.10.6.Word 5: Vendor specific data.


8.10.7.Word 6: Number of logical sectors per logical track

The number of user-addressable logical sectors per logical track in the default
translation mode.

8.10.8.Words 7-9: Vendor specific data.

8.10.9.Words 10-19: Serial Number

If word 10 of this field is 0000h, then the serial number is not specified and
the definition of the remaining words of this field are vendor specific.

If word 10 of this field is not equal to 0000h, then this field contains the
serial number of the device. The contents of this field is an ASCII character
string of twenty bytes.  The device shall pad the character string with spaces
(20h), if necessary, to ensure that the string is the proper length.

8.10.10.Word 20: Vendor specific data.

8.10.11.Word 21: Vendor specific data.

8.10.12.Word 22: Number of vendor specific bytes on READ/WRITE LONG commands

The contents of this field specifies the number of vendor specific bytes that
are appropriate for the device.  If the contents of this field are set to a
value other than 4, the SET FEATURES command should be used to switch the length
of READ LONG and WRITE LONG commands from 512 plus 4 to 512 plus the value
specified in this word.

8.10.13.Word 23-26: Firmware revision

If word 23 of this field is 0000h, then the firmware revision is not specified
and the definition of the remaining words of this field are vendor specific.

If word 23 of this field is not equal to 0000h, then this field contains the
firmware revision of the device. The contents of this field is an ASCII
character string of eight bytes.  The device shall pad the character string with
spaces (20h), if necessary, to ensure that the string is the proper length.

8.10.14.Words 27-46: Model number

If word 27 of this field is 0000h, then the model number is not specified and
the definition of the remaining words of this field are vendor specific.

If word 27 of this field is not equal to 0000h, then this field contains the
model number of the device. The contents of this field is an ASCII character
string of forty bytes.  The device shall pad the character string with spaces
(20h), if necessary, to ensure that the string is the proper length.

8.10.15.Word 47: READ/WRITE MULTIPLE support.

Bits 7-0 of this word define the maximum number of sectors per block that the
device supports for READ/WRITE MULTIPLE commands.  If a device supports the
READ/WRITE MULTIPLE and SET MULTIPLE MODE commands, these bits contain a non-
zero value.  If the device does not support the READ/WRITE MULTIPLE and SET
MULTIPLE MODE commands, these bits shall be zero.

8.10.16.Word 48: Reserved.

8.10.17.Word 49: Capabilities

8.10.17.1.Standby Timer Support

Bit 13 of word 49 is used to determine whether a device utilizes the Standby
Timer values defined in this standard.  If bit 13 is set to one, then the device
utilizes the Standby Timer values as specified in Table 13 (see clause 8.11).
If bit 13 is set to zero, the timer values utilized are vendor specific.

8.10.17.2.IORDY Support

Bit 11 of word 49 is used to help determine whether a device supports IORDY.  If
this bit is set to one, then the device supports IORDY operation.  If this bit
is zero, the device may support IORDY.  This insures backward compatibility.
If a device supports PIO Mode 3, then this bit shall be set.

8.10.17.3.IORDY Can Be Disabled

Bit 10 of word 49 is used to indicate a device's ability to enable or disable
the use of IORDY.  If this bit is set to one, then the device supports the
disabling of IORDY.  Control of IORDY is accomplished using the SET FEATURES
command.

8.10.17.4.LBA supported

Bit 9 of word 49 is used to indicate if the device supports LBA mode addressing.
If this bit is set, words 60-61 shall be valid.

8.10.17.5.DMA supported

Bit 8 of word 49 is used to indicate if the device supports the READ/WRITE DMA
commands.

8.10.18.Word 50: Reserved.

8.10.19.Word 51: PIO data transfer cycle timing mode

The PIO transfer timing for each ATA device falls into categories which have
unique parametric timing specifications.  To determine the proper device timing
category, compare the Cycle Time specified in figure 10 with the contents of
this field.  The value returned in Bits 15-8 should fall into one of the mode 0
through mode 2 categories specified in figure 10, and if it does not, then Mode
0 shall be used to serve as the default timing.  Note:  For backwards
compatibility with BIOSs written before Word 64 was defined for advanced modes,
a device reports in Word 51 the highest original PIO mode (i.e.  PIO mode 0, 1,
or 2) it can support.

8.10.20.Word 52: Single Word DMA data transfer cycle timing mode

The DMA transfer timing for each ATA device falls into categories which have
unique parametric timing specifications.  To determine the proper device timing
category, compare the Cycle Time specified in figure 11 with the contents of
this field.  The value returned in Bits 15-8 should fall into one of the
categories specified in figure 11 (i.e. 0, 1, or 2), and if it does not, then
Mode 0 shall be used to serve as the default timing.

The contents of this word shall be ignored if Words 62 or 63 are supported.



8.10.21.Word 53: Field Validity

If bit 0 of word 53 is set, then the values reported in words 54 through 58 are
valid.  If this bit is cleared, the values reported in words 54 through 58 may
be valid.  If bit 1 of word 53 is set, then the values reported in words 64
through 70 are valid.  If this bit is cleared, the values reported in words 64-
70 are not valid.  Any device which supports PIO Mode 3 or above, or supports
Multiword DMA Mode 1 or above, shall set bit 1 of word 53 and support the fields
contained in words 64 through 70.

8.10.22.Word 54: Number of current logical cylinders

The number of user-addressable logical cylinders in the current translation
mode.

Note:  For ATA-1 devices, if the INITIALIZE DEVICE PARAMETERS command has not
been issued to the device then the value of this word is vendor specific.

8.10.23.Word 55: Number of current logical heads

The number of user-addressable logical heads per logical cylinder in the current
translation mode.

Note:  For ATA-1 devices, if the INITIALIZE DEVICE PARAMETERS command has not
been issued to the device then the value of this word is vendor specific.

8.10.24.Word 56: Number of current logical sectors per logical track

The number of user-addressable logical sectors per logical track in the current
translation mode.

Note:  For ATA-1 devices, if the INITIALIZE DEVICE PARAMETERS command has not
been issued to the device then the value of this word is vendor specific.

8.10.25.Word 57-58: Current capacity in sectors

The current capacity in sectors excludes all sectors used for device-specific
purposes.  The value reported in this field shall be the product of words 54, 55
and 56.

8.10.26.Word 59: Multiple sector setting

If bit 8 is set, then bits 7-0 reflect the number of sectors currently set to
transfer on a READ/WRITE MULTIPLE command.  If word 47 bits 7-0 are zero then
word 59 bits 8-0 shall also be zero.

8.10.27.Word 60-61: Total number of user addressable sectors

If the device supports LBA Mode, these words reflect the total number of user
addressable sectors.  This value does not depend on the current device geometry.
If the device does not support LBA mode, these words shall be set to 0.

8.10.28.Word 62: Single word DMA transfer

The low order byte identifies by bit all of the Modes which are supported e.g.
if Mode 0 is supported, bit 0 is set.  The high order byte contains a single bit
set to indicate which mode is active.



8.10.29.Word 63: Multiword DMA transfer

The low order byte identifies by bit all of the Modes which are supported e.g.
if Mode 0 is supported, bit 0 is set.  The high order byte contains a single bit
set to indicate which mode is active.

8.10.30.Word 64: Flow Control PIO Transfer Modes Supported

Bits 7 through 0 of word 64 of the Identify Device parameter information is
defined as the Advanced PIO Data Transfer Supported Field.  This field is bit
significant.  Any number of bits may be set in this field by the device to
indicate which Advanced PIO Modes that it is capable of supporting.

Of these bits, bits 7 through 2 are Reserved for future Advanced PIO Modes.  Bit
0, if set, indicates that the device supports PIO Mode 3. Bit 1, if set,
indicates that the device supports PIO Mode 4.

Note:  For backwards compatibility with BIOSs written before Word 64 was defined
for advanced modes, a device reports in Word 51 the highest original PIO mode
(i.e.  PIO mode 0, 1, or 2) it can support.

8.10.31.Word 65: Minimum Multiword DMA Transfer Cycle Time Per Word

Word 65 of the parameter information of the IDENTIFY DEVICE command is defined
as the Minimum Multiword DMA Transfer Cycle Time Per Word.  This field defines,
in nanoseconds, the minimum cycle time that the device can support when
performing Multiword DMA transfers on a per word basis.

If this field is supported, bit 1 of word 53 shall be set.  Any device which
supports Multiword DMA Mode 1 or above shall support this field, and the value
in word 65 shall not be less than the minimum cycle time reported by the fastest
DMA mode supported by the device.

If bit 1 of word 53 is set because a device supports a field in Words 64-70
other than this field and the device does not support this field, the device
shall return a value of zero in this field.

8.10.32.Word 66: Manufacturer's Recommended Multiword DMA Cycle Time

Word 66 of the parameter information of the IDENTIFY DEVICE command is defined
as the Manufacturer's Recommended Multiword DMA Transfer Cycle Time.  This field
defines, in nanoseconds, the minimum cycle time per word during a single sector
host transfer while performing a multiple sector READ DMA or WRITE DMA commands
over all locations on the media under nominal conditions.  If a host runs at a
faster cycle rate by operating at a cycle time of less than this value, the
device may negate DMARQ for flow control.  The rate at which DMARQ is negated
could result in reduced throughput despite the faster cycled rate.  Transfer at
this rate does not ensure that flow control will not be used, but implies that
higher performance MAY result.

If this field is supported, bit 1 of word 53 shall be set.  Any device which
supports Multiword DMA Mode 1 or above shall support this field, and the value
in word 66 shall not be less than the value in word 65.

If bit 1 of word 53 is set because a device supports a field in Words 64-70
other than this field and the device does not support this field, the device
shall return a value of zero in this field.



8.10.33.Word 67: Minimum PIO Transfer Cycle Time Without Flow Control

Word 67 of the parameter information of the IDENTIFY DEVICE command is defined
as the Minimum PIO Transfer Without Flow Control Cycle Time.  This field
defines, in nanoseconds, the minimum cycle time that, if used by the host, the
device guarantees data integrity during the transfer without utilization of flow
control.

Any device may support this field, and if this field is supported, Bit 1 of word
53 shall be set.

Any device which supports PIO Mode 3 or above shall support this field, and the
value in word 67 shall not be less than the value reported in word 68.

If bit 1 of word 53 is set because a device supports a field in Words 64-70
other than this field and the device does not support this field, the device
shall return a value of zero in this field.

8.10.34.Word 68: Minimum PIO Transfer Cycle Time With IORDY

Word 68 of the parameter information of the IDENTIFY DEVICE command is defined
as the Minimum PIO Transfer With IORDY Flow Control Cycle Time.  This field
defines, in nanoseconds, the minimum cycle time that the device can support
while performing data transfers while utilizing IORDY flow control.

Any device may support this field, and if this field is supported, Bit 1 of word
53 shall be set.

Any device which supports PIO Mode 3 or above shall support this field, and the
value in word 68 shall not be less than the fastest PIO mode reported by the
device.

If bit 1 of word 53 is set because a device supports a field in Words 64-70
other than this field and the device does not support this field, the device
shall return a value of zero in this field.

8.10.35.Words 69-70: Reserved for future PIO modes.

Words 69 and 70 are reserved for future advanced PIO modes

8.10.36.Words 71-127: Reserved.

8.10.37.Words 128-159: Vendor specific.

8.10.38.Words 160-255: Reserved.



8.11.IDLE

OPCODE - 97h or E3h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS - The value in the Sector Count register when the IDLE command is issued
shall determine the time period programmed into the Standby Timer.  See Table
13.

+---------------------+------------------------------+
| Sector Count        | Corresponding                |
| Register contents   | Timeout Period               |
+---------------------+------------------------------+
|   0       (00h)     | Timeout Disabled             |
|   1 - 240 (01h-F0h) | (value * 5) seconds          |
| 241 - 251 (F1h-FBh) | ((value - 240) * 30) minutes |
| 252       (FCh)     | 21 minutes                   |
| 253       (FDh)     | Vendor unique period between |
|                     | 8 and 12 hours               |
| 254       (FEh)     | Reserved                     |
| 255       (FFh)     | 21 minutes 15 seconds        |
+---------------------+------------------------------+
Table 13 - Automatic Standby Timer Periods


NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command - The device does not support the Power
Management command set.

PREREQUISITES - None.

DESCRIPTION - This command causes the device to set the BSY bit, enter the Idle
Mode, clear the BSY bit, and assert INTRQ.  INTRQ is asserted even though the
device may not have fully transitioned to Idle Mode.

If the Sector Count register is non-zero then the Standby Timer shall be
enabled.  The value in the Sector Count register shall be used to determine the
time programmed into the Standby Timer.

If the Sector Count register is zero then the Standby Timer is disabled.



8.12.IDLE IMMEDIATE

OPCODE - 95h or E1h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS - None.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command - The device does not support the Power
Management command set.

PREREQUISITES - None.

DESCRIPTION - This command causes the device to set the BSY bit, enter the Idle
Mode, clear the BSY bit, and assert INTRQ.  INTRQ is asserted even though the
device may not have fully transitioned to Idle Mode.


8.13.INITIALIZE DEVICE PARAMETERS

OPCODE - 91h

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - The Sector Count register specifies the number of logical sectors per
logical track, and the Device/Head register which specifies the number of
logical heads minus 1.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the device does not support the requested CHS
translation.

Note:  Previous ATA specifications were unclear about the error conditions that
this command may indicate.  Some implementations do not indicate any errors for
this command even when the command fails.  However, most of these
implementations do fail media access commands if a valid CHS translation is not
in effect.

PREREQUISITES - None.

DESCRIPTION - This command enables the host to set the number of logical sectors
per track and the number of logical heads minus 1, per logical cylinder for the
current CHS translation mode.

Upon receipt of the command, the device sets the BSY bit, saves the parameters,
clears the BSY bit, and generates an interrupt.

A device shall support the CHS translation described in words 1, 3 and 6 of the
IDENTIFY DEVICE information.  Support of other CHS translations is optional.

If the requested CHS translation is not supported, the device shall set the
Error bit in the Status register and set the Aborted Command bit in the Error
register before clearing the BSY bit in the Status register.

If the requested CHS translation is not supported, the device shall fail all
media access commands with an ID Not Found error until a valid CHS translation
is established.

Note:  Host implementations should use the default CHS translation mode
described in words 1, 3 and 6 of the IDENTIFY DEVICE information.  Future ATA
specifications may restrict the valid input parameters for this command to these
values.

Note:  Some ATA-1 devices require that this command be issued prior to media
access.


8.14.MEDIA EJECT (removable)

OPCODE - EDh

TYPE - Optional.

PROTOCOL - Non-data.

INPUTS - None required.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - If the device does not support this command, the device shall
return a Command Abort error.

PREREQUISITES - None.

DESCRIPTION - This command completes any pending operations, spins down the
device if needed, unlocks the door or media if locked, and initiates a media
eject, if required.




8.15.NOP

OPCODE - 00h

TYPE - Optional.

PROTOCOL - Non-data.

INPUTS - None required.

NORMAL OUTPUTS - The Command Block registers, other than the Error and Status
registers, are not changed by this command.

ERROR OUTPUTS - This command always fails with a Aborted Command error.

PREREQUISITES - None.

DESCRIPTION - This command enables a host which can only perform 16-bit register
accesses to check device status.  The device shall respond as it does to an
unrecognized command by setting Aborted Command in the Error register, Error in
the Status register, clearing Busy in the Status register, and asserting INTRQ.
NOTE:  When a 16-bit host writes to the Device/Head Register, one byte contains
the Command register, so the device sees a new command when the intended purpose
is only to select a device.  Both devices may be Busy but not necessarily Ready,
e.g.  Device 0 may be ready, but not device 1. To check this possibility a
typical sequence for an 8-bit host would be:
  a)  Read the Status register (wait until Busy False)
  b)  Select the device (write to the Device/Head Register)
  c)  Read the Status register (wait until Busy False and Ready True)
  d)  Send the command (write to the Command register).

As a 16-bit host executes b and d simultaneously, a problem occurs if the device
being selected is Not Ready at the time the command is issued.



8.16.READ BUFFER

OPCODE - E4h

TYPE - Optional.

PROTOCOL - PIO data in.

INPUTS - None required.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported.

PREREQUISITES - None.

Note:  A WRITE BUFFER command should immediately proceed a READ BUFFER command.

DESCRIPTION - The READ BUFFER command enables the host to read the current
contents of the device's sector buffer.  When this command is issued, the device
sets the BSY bit, sets up the sector buffer for a read operation, sets the DRQ
bit, clears the BSY bit, and generates an interrupt.  The host then reads the
data from the buffer.

The READ BUFFER and WRITE BUFFER commands shall be synchronized such that
sequential WRITE BUFFER and READ BUFFER commands access the same 512 bytes
within the buffer.



8.17.READ DMA (with retries and without retries)

OPCODE - C8h (with retries) or C9h (without retries)

TYPE - Optional.

PROTOCOL - DMA.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number
registers specify the starting sector address to be read.  The Sector Count
register specifies the number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - The host shall initialize the DMA channel.

DESCRIPTION - This command executes in a similar manner to the READ SECTOR(S)
command except for the following:
ù       the host initializes the DMA channel prior to issuing the command
ù       data transfers are qualified by DMARQ and are performed by the DMA channel
ù       the device issues only one interrupt per command to indicate that data
transfer has terminated and status is available.

During the DMA transfer phase of a Read DMA command, the device shall provide
status of the BSY bit or the DRQ bit until the command is completed.

The with retries and without retries versions of this command differ in
operation only in the level of error recovery performed by the device.  The
level of error recovery performed by the device for either command is vendor
specific.



8.18.READ LONG (with retries and without retries)

OPCODE - 22h (with retries) or 23h (without retries)

TYPE - Optional.

PROTOCOL - PIO data in.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be read.  The Sector Count register shall not
specify a value other than 1.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - The SET FEATURES subcommand to enable more than 4 vendor
specific bytes shall be executed prior to the READ LONG command if other than 4
vendor specific bytes are to be transferred.

DESCRIPTION - The READ LONG command performs similarly to the READ SECTOR(S)
command except that it returns the data and a number of vendor specific bytes
appended to the data field of the desired sector.  During a READ LONG command,
the device does not check to determine if there has been a data error.  Only
single sector read long operations are supported.

The transfer of the vendor specific bytes shall be one byte at a time over bits
DD0-7 only (8-bits wide).

The with retries and without retries versions of this command differ in
operation only in the level of error recovery performed by the device.  The
level of error recovery performed by the device for either command is vendor
specific.

Note:  Some ATA-1 devices are not capable of delivering the 8 bit ECC
immediately after the word sector data.  BIOS and driver developers should use
PIO mode 0 for 8 bit ECC accesses.


8.19.READ MULTIPLE

OPCODE - C4h

TYPE - Optional.

PROTOCOL - PIO data in.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be read.  The Sector Count register specifies the
number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - A successful SET MULTIPLE MODE command shall proceed a READ
MULTIPLE command.

DESCRIPTION - The READ MULTIPLE command performs similarly to the READ SECTOR(S)
command.  Interrupts are not generated on every sector, but on the transfer of a
block which contains the number of sectors defined by a SET MULTIPLE MODE
command.  Command execution is identical to the READ SECTOR(S) operation except
that the number of sectors defined by a SET MULTIPLE MODE command are
transferred without intervening interrupts.  The DRQ bit qualification of the
transfer is required only at the start of the data block, not on each sector.

The block count of sectors to be transferred without intervening interrupts is
programmed by the SET MULTIPLE MODE command, which shall be executed prior to
the READ MULTIPLE command.  When the READ MULTIPLE command is issued, the Sector
Count register contains the number of sectors (not the number of blocks or the
block count) requested.

If the number of requested sectors is not evenly divisible by the block count,
as many full blocks as possible are transferred, followed by a final, partial
block transfer.  The partial block transfer shall be for n sectors, where n =
remainder (SECTOR COUNT / block count)

If the READ MULTIPLE command is attempted before the SET MULTIPLE MODE command
has been executed or when READ MULTIPLE commands are disabled, the READ MULTIPLE
operation shall be rejected with an Aborted Command error.

Device errors encountered during READ MULTIPLE commands are posted at the
beginning of the block or partial block transfer, but the DRQ bit is still set
and the data transfer shall take place as it normally would, including transfer
of corrupted data, if any.
The contents of the Command Block Registers following the transfer of a data
block which had a sector in error are undefined.  The host should retry the
transfer as individual requests to obtain valid error information.

Subsequent blocks or partial blocks are transferred only if the error was a
correctable data error.  All other errors cause the command to stop after
transfer of the block which contained the error.  Interrupts are generated when
the DRQ bit is set at the beginning of each block or partial block.



8.20.READ SECTOR(S) (with retries and without retries)

OPCODE - 20h (with retries) or 21h (without retries)

TYPE - Mandatory.

PROTOCOL - PIO data in.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be read.  The Sector Count register specifies the
number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - None.

DESCRIPTION - This command reads from 1 to 256 sectors as specified in the
Sector Count register.  A SECTOR COUNT of 0 requests 256 sectors.  The transfer
begins at the sector specified in the Sector Number register.

The DRQ bit is always set prior to data transfer regardless of the presence or
absence of an error condition.

The with retries and without retries versions of this command differ in
operation only in the level of error recovery performed by the device.  The
level of error recovery performed by the device for either command is vendor
specific.


8.21.READ VERIFY SECTOR(S) (with retries and without retries)

OPCODE - 40h (with retries) or 41h (without retries)

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be verified.  The Sector Count register specifies
the number of sectors to be verified.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - None.

DESCRIPTION - This command is identical to the READ SECTOR(S) command, except
that the DRQ bit is never set, and no data is transferred to the host.

When the requested sectors have been verified, the device clears the BSY bit and
generates an interrupt.

The with retries and without retries versions of this command differ in
operation only in the level of error recovery performed by the device.  The
level of error recovery performed by the device for either command is vendor
specific.


8.22.RECALIBRATE

OPCODE - 10h through 1Fh

TYPE - Optional.

PROTOCOL - Non-data.

INPUTS - None.

NORMAL OUTPUTS - If the command is executed in CHS addressing mode, Cylinder
High, Cylinder Low and the head portion of Device/Head shall be zero.  The
Sector Number register shall be 1. If the command is executed in LBA addressing
mode, the Cylinder High, Cylinder Low, the head portion of the Device/Head and
the Sector Number register shall be zero.

ERROR OUTPUTS - If the device cannot reach cylinder 0, a Track 0 Not Found error
is posted.

PREREQUISITES - None.

DESCRIPTION - The function performed by this command is vendor specific.



8.23.SEEK

OPCODE - 70h through 7Fh

TYPE - Mandatory.

PROTOCOL - Non-data.

INPUTS - The Cylinder High, Cylinder Low, head portion of the Device/Head
register and the Sector Number register contain the sector address to which the
device should move the read/write heads.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - None.

DESCRIPTION - The function performed by this command is vendor specific.


8.24.SET FEATURES

OPCODE - EFh

TYPE - The command is optional and if implemented each subcommand is optional.

PROTOCOL - Non-data.

INPUTS - The Feature register contains a subcommand code as described in table
14.  Some subcommands use other registers, such as the Sector Count register to
pass additional information to the device.

NORMAL OUTPUTS - See the subcommand descriptions.

ERROR OUTPUTS - If the device does not support the command or if any input value
is not supported or is invalid, the device posts an Aborted Command error.

PREREQUISITES - None.

DESCRIPTION - This command is used by the host to establish the following
parameters which affect the execution of certain device features as shown in
table 14.

+=====+=============================================================+
| 01h | Enable 8-bit data transfers (see 6.2.5)                     |
| 02h | Enable write cache *                                        |
| 03h | Set transfer mode based on value in Sector Count register   |
| 33h | Disable retry *                                             |
| 44h | Length of vendor specific bytes on READ LONG/WRITE LONG cmds|
| 54h | Set cache segments to Sector Count register value *         |
| 55h | Disable read look-ahead feature                             |
| 66h | Disable reverting to power on defaults (see 8.25)           |
| 77h | Disable ECC *                                               |
| 81h | Disable 8-bit data transfers (see 6.2.5)                    |
| 82h | Disable write cache *                                       |
| 88h | Enable ECC *                                                |
| 99h | Enable retries *                                            |
| AAh | Enable read look-ahead feature                              |
| ABh | Set maximum prefetch using Sector Count register value *    |
| BBh | 4 bytes of vendor specific byts on READ LONG/WRITE LONG cmds|
| CCh | Enable reverting to power on defaults (see 8.25)            |
|-----+-------------------------------------------------------------|
|     |  *These feature definitions are vendor specific             |
+=====+=============================================================+
Table 14 - Set Features register Definitions

All values not contained in Table 14 are reserved for future definition.

At power on, or after a hardware reset, the default setting of the functions
specified by the subcommands are vendor specific.

A setting of 66h allows settings of greater than 80h which may have been
modified since power on to remain at the same setting after a software reset.

A host can choose the transfer mechanism by Set Transfer Mode and specifying a
value in the Sector Count register.  The upper 5 bits define the type of
transfer and the low order 3 bits encode the mode value.

  PIO Default Transfer Mode                             00000 000
  PIO Default Transfer Mode, Disable IORDY      00000 001
  PIO Flow Control Transfer Mode x                      00001 nnn
  Single Word DMA Mode x                                00010 nnn
  Multiword DMA Mode x                                  00100 nnn
  Reserved                                                      01000 nnn
  Reserved                                                      10000 nnn

where "nnn" is a valid mode number in binary and "x" is the mode number in
decimal for the associated transfer type.
(Editor's note:  It is intended that the reserved values be used for future
specification of an alternative flow control mechanism.)

If a device supports this specification, and receives a SET FEATURES command
with a Set Transfer Mode parameter and a Sector Count register value of "00000
000", it shall set its default PIO transfer mode.  If the value is "00000 001"
and the device supports disabling of IORDY, then the device shall set its
default PIO transfer mode and disable IORDY.

See vendor specification for the default mode of the commands which are vendor
specific.

Devices reporting support for Multi Word DMA Transfer Mode 1 shall also support
Multi Word DMA Transfer Mode 0.  Support of IORDY is mandatory when PIO Mode 3
or above is the current mode of operation.


8.25.SET MULTIPLE MODE

OPCODE - C6h

TYPE - Optional.

PROTOCOL - Non-data.

INPUTS - The Sector Count register contains number of sectors per block to use
on all following READ/WRITE MULTIPLE commands.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - If the device does not support the READ/WRITE MULTIPLE and SET
MULTIPLE MODE commands or if a block count is not supported, a Aborted Command
error is posted, and READ MULTIPLE and WRITE MULTIPLE commands are disabled.

PREREQUISITES - None.

DESCRIPTION - This command enables the device to perform READ AND WRITE MULTIPLE
operations and establishes the block count for these commands.

Devices shall support the block size specified in the IDENTIFY DRIVE parameter
word 47, bits 7 through 0, and may also support smaller values.

Upon receipt of the command, the device sets the BSY bit equal to one and checks
the Sector Count register.  If the Sector Count register contains a valid value
and the block count is supported, the value is used for all subsequent READ
MULTIPLE and WRITE MULTIPLE commands and their execution is enabled.

If the Sector Count register contains 0 when the command is issued, READ AND
WRITE MULTIPLE commands are disabled.

At power on, or after a hardware reset, the default mode is READ AND WRITE
MULTIPLE disabled.  Following a software reset, the READ and WRITE MULTIPLE
commands may be enabled or disabled.  The SET FEATURES command Disable Reverting
To Power on Defaults and Enable Reverting To Power on Defaults subcommands, if
supported, can be used to control the results of a software reset.


8.26.SLEEP

OPCODE - 99h or E6h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS - None.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command - The device does not support the Power
Management command set.

PREREQUISITES - None.

DESCRIPTION - This command is the only way to cause the device to enter Sleep
Mode.

This command causes the device to set the BSY bit, prepare to enter Sleep mode,
clear the BSY bit and assert INTRQ.  The host shall read the Status register in
order to clear the interrupt and allow the device to enter Sleep mode.  In Sleep
mode the interface becomes inactive without affecting the operation of the ATA
interface.  The host shall not attempt to access the Command Block registers
while the device is in Sleep mode.

Because some host systems may not read the Status register and clear the
interrupt, a device may automatically deassert INTRQ and enter Sleep mode after
a vendor specified time period of not less than 2 seconds.

The only way to recover from Sleep Mode is with a software reset or a hardware
reset.

A device shall not power on in Sleep Mode nor remain in Sleep Mode following a
reset sequence.


8.27.STANDBY

OPCODE - 96h or E2h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS - The value in the Sector Count register when the STANDBY command
is issued shall determine the time period programmed into the Standby
Timer.  See Table 13 in clause 8.11.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the device does not support the Power
Management command set.

PREREQUISITES - None.

DESCRIPTION - This command causes the device to set the BSY bit, enter the
Standby Mode, clear the BSY bit, and assert INTRQ.  INTRQ is asserted even
though the device may not have fully transitioned to Standby Mode.

If the Sector Count register is non-zero then the Standby Timer shall be
enabled.  The value in the Sector Count register shall be used to determine the
time programmed into the Standby Timer.

If the Sector Count register is zero then the Standby Timer is disabled.



8.28.STANDBY IMMEDIATE

OPCODE - 94h or E0h

TYPE - Optional - Power Management Feature Set.

PROTOCOL - Non-data command.

INPUTS - None.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command - The device does not support the Power
Management command set.

PREREQUISITES - None.

DESCRIPTION - This command causes the device to set the BSY bit, enter the
Standby Mode, clear the BSY bit, and assert INTRQ.  INTRQ is asserted even
though the device may not have fully transitioned to Standby Mode.



8.29.WRITE BUFFER

OPCODE - E8h

TYPE - Optional.

PROTOCOL - PIO data out.

INPUTS - None.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported.

PREREQUISITES - None.

DESCRIPTION - This command enables the host to overwrite the contents of one
sector in the device's buffer. When this command is issued, the device sets the
BSY bit, sets up the buffer for a write operation, sets the DRQ bit, clears the
BSY bit, and waits for the host to write the data.  Once the host has written
the data, the device sets the BSY bit, clears the BSY bit and generates an
interrupt.

The READ BUFFER and WRITE BUFFER commands shall be synchronized within the
device such that sequential WRITE BUFFER and READ BUFFER commands access the
same 512 bytes within the buffer.


8.30.WRITE DMA (with retries and without retries)

OPCODE - CAh (with retries) or CBh (without retries)

TYPE - Optional.

PROTOCOL - DMA.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be written.  The Sector Count register specifies
the number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - The host shall initialize the DMA channel.

DESCRIPTION - This command executes in a similar manner to WRITE SECTOR(S)
except for the following:

ù       the host initializes the DMA channel prior to issuing the command
ù       data transfers are qualified by DMARQ and are performed by the DMA channel
ù       the device issues only one interrupt per command to indicate that data
transfer has terminated and status is available.

During the execution of a Write DMA command, the device shall provide status of
the BSY bit or the DRQ bit until the command is completed.

The with retries and without retries versions of this command differ in
operation only in the level of error recovery performed by the device.  The
level of error recovery performed by the device for either command is vendor
specific.


8.31.WRITE LONG (with retries and without retries)

OPCODE - 32h (with retries) or 33h (without retries)

TYPE - Optional.

PROTOCOL - PIO data out.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be written.  The Sector Count register shall not
specify a value other than 1.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - The SET FEATURES subcommand to enable other than 4 vendor
specific bytes shall be executed prior to the WRITE LONG command if other than 4
vendor specific bytes are to be transferred.

DESCRIPTION - This command is similar to the WRITE SECTOR(S) command except that
it writes the data and the vendor specific bytes as supplied by the host; the
device does not generate the vendor specific bytes itself.  Only single sector
Write Long operations are supported.

The transfer of the vendor specific bytes shall be one byte at a time over bits
DD0-7 only (8-bits wide).

The with retries and without retries versions of this command differ in
operation only in the level of error recovery performed by the device.  The
level of error recovery performed by the device for either command is vendor
specific.


8.32.WRITE MULTIPLE

OPCODE - C5h

TYPE - Optional.

PROTOCOL - PIO data out.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be written.  The Sector Count register specifies
the number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - A successful SET MULTIPLE MODE command shall proceed a WRITE
MULTIPLE command.

DESCRIPTION - This command is similar to the WRITE SECTOR(S) command. interrupts
are not generated on every sector, but on the transfer of a block which contains
the number of sectors defined by SET MULTIPLE MODE.

Command execution is identical to the WRITE SECTOR(S) operation except that the
number of sectors defined by the SET MULTIPLE MODE command are transferred
without intervening interrupts.  The DRQ bit qualification of the transfer is
required only at the start of the data block, not on each sector.

The block count of sectors to be transferred without intervening interrupts is
programmed by the SET MULTIPLE MODE command, which shall be executed prior to
the WRITE MULTIPLE command.

When the WRITE MULTIPLE command is issued, the Sector Count register contains
the number of sectors (not the number of blocks or the block count) requested.

If the number of requested sectors is not evenly divisible by the block count,
as many full blocks as possible are transferred, followed by a final, partial
block transfer.  The partial block transfer is for n sectors, where n =
Remainder (SECTOR COUNT / block count).

If the WRITE MULTIPLE command is attempted before the SET MULTIPLE MODE command
has been executed or when WRITE MULTIPLE commands are disabled, the Write
Multiple operation shall be rejected with an Aborted Command error.

Device errors encountered during WRITE MULTIPLE commands are posted after the
attempted device write of the block or partial block transferred.  The Write
command ends with the sector in error, even if it was in the middle of a block.
Subsequent blocks are not transferred in the event of an error.

The contents of the Command Block Registers following the transfer of a data
block which had a sector in error are undefined.  The host should retry the
transfer as individual requests to obtain valid error information.  Interrupts
are generated when the DRQ bit is set at the beginning of each block or partial
block.


8.33.WRITE SAME

OPCODE - E9h

TYPE - Optional.

PROTOCOL - PIO data out.

INPUTS - The Feature register contains a sub command code, either 22H or DDH.
If the Feature register contains 22H, the Cylinder Low, Cylinder High,
Device/Head and Sector Number specify the starting sector address to be written.
The Sector Count register specifies the number of sectors to be written (not the
number of sectors transferred by the host).  If the Feature register contains
code DDH, the Cylinder High, Cylinder Low, head portion of the Device/Head,
Sector Number and Sector Count registers are not used.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

NORMAL OUTPUTS - If no error, the Cylinder Low, Cylinder High, Device/Head and
Sector Number registers specify the address of the last sector written.  If the
command ends with an error, these registers contain the address of the sector
where the first error was detected and the Sector Count register contains the
number of sectors remaining to be transferred in order to complete the original
request.

ERROR OUTPUTS - If the Feature register contains a value other than 22h or DDh,
the command shall be rejected with an aborted command error.  Other errors
possible are Bad Block, Uncorrectable Data Error, ID Not Found and Address Mark
Not Found.

PREREQUISITES - None.

DESCRIPTION - This command executes in a similar manner to WRITE SECTOR(S)
except that only one sector of data is transferred.  The contents of the sector
are written to the media one or more times.

NOTE:  The WRITE SAME command allows for initialization of part or all of the
medium to the specified data with a single command.

If the Features register is 22h, the device shall write that part of the medium
specified by the Sector Number and sector address registers.

The support of the Features register value of DDh is optional.  If the Features
register contains DDh and is supported, the device shall initialize all the user
accessible media.

The device issues an interrupt to indicate that the command is complete.  Any
error encountered during execution results in the termination of the write
operation.

It is recommend that system implementations not utilize this command.



8.34.WRITE SECTOR(S) (with retries and without retries)

OPCODE - 30h (with retries) or 31h (without retries)

TYPE - Mandatory.

PROTOCOL - PIO data out.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be written.  The Sector Count register specifies
the number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - None.

DESCRIPTION - This command writes from 1 to 256 sectors as specified in the
Sector Count register.  A SECTOR COUNT of 0 requests 256 sectors.

The with retries and without retries versions of this command differ in
operation only in the level of error recovery performed by the device.  The
level of error recovery performed by the device for either command is vendor
specific.



8.35.WRITE VERIFY

OPCODE - 3Ch

TYPE - Optional.

PROTOCOL - PIO data out.

INPUTS - The Cylinder Low, Cylinder High, Device/Head and Sector Number specify
the starting sector address to be written.  The Sector Count register specifies
the number of sectors to be transferred.

NORMAL OUTPUTS - None required.

ERROR OUTPUTS - Aborted Command if the command is not supported. An
unrecoverable error encountered during the execution of this command results in
the termination of the command and the Command Block registers contain the
sector address of the sector where the first unrecoverable error occurred.

PREREQUISITES - None.

DESCRIPTION - This command is similar to the WRITE SECTOR(S) command, except
that each sector is verified from the media after being written and before the
command is completed.


9.      Protocol

Commands can be grouped into different classes according to the protocols
followed for command execution.  The command classes with their associated
protocols are defined below.

For all commands, the host first checks if the BSY bit is equal to one, and
should proceed no further unless and until the BSY bit is equal to zero.  For
most commands, the host shall also wait for the DRDY bit to be equal to one
before proceeding.  The commands shown with DRDY=x can be executed when the DRDY
bit is equal to zero.

Data transfers may be accomplished in more ways than are described below, but
these sequences should work with all known implementations of ATA devices.

A device shall maintain either the BSY bit equal to one or the DRQ bit equal to
one at all times until the command is completed.  The INTRQ signal is used by
the device to signal most, but not all, times when the BSY bit is changed from 1
to 0 during command execution.

A command shall only be interrupted with a hardware or software reset.  The
result of writing to the Command register while the BSY bit is equal to one or
the DRQ bit is equal to one is unpredictable and may result in data corruption.
A command should only be interrupted by a reset at times when the host thinks
there may be a problem, such as a device that is no longer responding.  Host
programmers are warned against setting unrealistically short command timeout
periods since this may impact a device's ability to perform device level retry
and data recovery activities.




9.1.    Power on and hardware resets

This clause describes the algorithm and timing relationships for Devices 0 and 1
during the processing of power on and hardware resets.

The timing assumes the following:

a) DASP- is asserted by Device 1 and received by Device 0 at  power-on or
hardware reset to indicate the presence of Device 1.  At all other times it
is asserted by Device 0 or Device 1 to indicate when a device is active.
b) PDIAG- is asserted by Device 1 and detected by Device 0. It is used by Device
1 to indicate to Device 0 that it has completed diagnostics without error and
is ready to accept commands from the Host (BSY bit is cleared).  This does
not indicate that the device is ready, only that it can accept commands.

9.1.1. Power on and hardware resets - device 0

a) Host asserts RESET- for a minimum of 25 usec.
b) Device 0 sets the BSY bit no later than 400 nsec after RESET- is negated.
c) Device 0 negates DASP- no later than 1 msec after RESET- is negated.
d) Device 0 samples for at least 450 msec for DASP- to be asserted from Device
1. This sampling starts 1 ms after RESET- is negated.
e) Device 0 performs hardware initialization and diagnostics.
f) Device 0 may revert to its default condition.
g) If Device 0 detected that DASP- was asserted during step d), then Device 0
waits up to 31 seconds for Device 1 to assert PDIAG-.  If PDIAG- is asserted
within 31 seconds, Device 0 sets bit 7 equal to 0 in the Error Register, else
Device 0 sets bit 7 equal to 1 in the Error Register.  If DASP- assertion was
not detected in step d) Device 0 sets bit 7 equal to 0 in the Error Register.
In either case the device shall set the Sector Count register to 01h, the
Sector Number register to 01h, the Cylinder Low register to 00h, the Cylinder
High register to 00h, and the Device/Head register to 00h.
Device 0 shall store whether or not Device 1 was detected in step d) because
this information is need in order to process any Software reset or EXECUTE
DEVICE DIAGNOSTIC command later.
h) Device 0 posts diagnostic results to bits 6-0 of the Error Register.
i) Device 0 clears the BSY bit when ready to accept commands that do not require
the DRDY bit to be equal to 1.  Device 0 shall clear the BSY bit no later
than 31 seconds from the time that RESET- is negated.
j) Device 0 sets the DRDY bit when ready to accept any command.
NOTE:  Steps i) and j) may occur at the same time.  While no maximum time is
specified for the DRDY bit to be set to 1, a host should allow up to 2
minutes for the DRDY bit to become 1.  See Figure 8.

9.1.2. Power on and hardware resets - device 1

a) Host asserts RESET- for a minimum of 25 usec.
b) Device 1 sets the BSY bit no later than 400 nsec after RESET- is negated.
c) Device 1 negates DASP- no later than 1 msec after RESET- is negated.
d) Device 1 negates PDIAG- before asserting DASP-.
e) Device 1 asserts DASP- no later than 400 msecs after RESET- is negated.
f) Device 1 performs hardware initialization and diagnostics.
g) Device 1 may revert to its default condition.
h) Device 1 posts diagnostic results to the Error Register.
i) Device 1 clears the BSY bit when ready to accept commands that do not require
the DRDY bit to be equal to 1.
j) If Device 1 passed its diagnostics without error in step f), Device 1 asserts
PDIAG-.  If the diagnostics failed, Device 1 does not assert PDIAG- and
continues to the next step.  Device 1 shall clear the BSY bit, and optionally
assert PDIAG-, no later than 30 seconds from the time RESET- is negated.  The
device shall set the Sector Count register to 01h, the Sector Number register
to 01h, the Cylinder Low register to 00h, the Cylinder High register to 00h,
and the Device/Head register to 00h.
k) Device 1 sets the DRDY bit when ready to accept any command.
NOTE:  Steps i), j) and k) may occur at the same time.  While no maximum time
is specified for the DRDY bit to be set to 1, a host should allow up to 2
minutes for the DRDY bit to become 1.  See Figure 8.
l) Device 1 negates DASP- after the first command is received or negates DASP-
if no command is received within 31 seconds after RESET- is asserted.

              __
   RESET- ___/  \_________________________________________
               ____________________
   BSY    ____/                    \______________________
                                                       ___
   DRDY   ____________________________________________/

                |<---------------->|<---------------->|
                  Max for device 0    Minimum time is
                   is 31 seconds.     0 seconds.
                  Max for device 1    No maximum time
                   is 30 seconds.     is specified.

Figure 8 - BSY and DRDY timing for power on and hardware resets


9.2.    Software reset

This clause describes the algorithm and timing relationships for Devices 0 and 1
during the processing of software resets.

9.2.1. Software reset - device 0

a) Host sets the SRST bit to 1 in the Device Control register.
b) Device 0 sets BSY bit no later than 400 nsec after detecting that the SRST
bit is equal to 1.
c) Device 0 performs hardware initialization and diagnostics.
d) Device 0 may revert to its default condition.
e) Device 0 posts diagnostic results to the Error Register.
f) Device 0 waits for the host to set the SRST bit to 0.
g) If Device 0 detected that Device 1 is present during the most recent power on
or hardware reset sequence, then Device 0 waits up to 31 seconds from the
time that the SRST bit to become 0 for Device 1 to assert PDIAG-.  If PDIAG-
is asserted within 31 seconds, Device 0 sets bit 7 equal to 0 in the Error
Register, else Device 0 sets bit 7 equal to 1 in the Error Register.  If
device 1 was not detected during the most recent power up or hardware reset
sequence, then Device 0 sets bit 7 equal to 0 in the Error register. In
either case the device shall set the Sector Count register to 01h, the Sector
Number register to 01h, the Cylinder Low register to 00h, the Cylinder High
register to 00h, and the Device/Head register to 00h.
h) Device 0 clears the BSY bit when ready to accept commands that do not require
the DRDY bit to be equal to 1.  Device 0 shall clear the BSY bit no later
than 31 seconds from the time that the host sets the SRST bit equal to 0.
Note:  Steps g) and h) may occur very rapidly.
i) Device 0 sets the DRDY bit when ready to accept any command.
NOTE:  Steps h) and i) may occur at the same time.  While no maximum time is
specified for the DRDY bit to become equal to 1 to occur, a host should allow
up to 2 minutes for the DRDY bit to be set to 1.  See Figure 9.

9.2.2. Software reset - device 1

a) Host sets SRST bit to 1 in the Device Control register.
b) Device 1 set the BSY bit no later than 400 nsec after detecting that the SRST
bit to equal to 1.
c) Device 1 negates PDIAG- no later than 1 msec after detecting that the SRST
bit is 1.
d) Device 1 perform hardware initialization and diagnostics.
e) Device 1 may revert to its default condition.
f) Device 1 posts diagnostic results to the Error Register.
g) Device 1 waits for the host to set the SRST bit equal to 0.
h) Device 1 clears the BSY bit when ready to accept commands that do not require
the DRDY bit to be equal to 1.
i) If Device 1 passed its diagnostics without error in step d), Device 1 asserts
PDIAG-.  If the diagnostics failed, Device 1 does not assert PDIAG- and
continues to the next step.  Device 1 shall clear the BSY bit, optionally
assert PDIAG-, no later than 30 seconds from the time the host sets the SRST
bit to 0. The device shall set the Sector Count register to 01h, the Sector
Number register to 01h, the Cylinder Low register to 00h, the Cylinder High
register to 00h, and the Device/Head register to 00h.
j) Device 1 sets the DRDY bit when ready to accept any command.
NOTE:  Steps h), i) and j) may occur at the same time.  While no maximum time
is specified for the DRDY bit to be set to 1, a host should allow up to 2
minutes for the DRDY bit to become 1.  See Figure 9.

            __
   SRST ___/  \_________________________________________
            _____________________
   BSY  ___/                     \______________________
                                                     ___
   DRDY ____________________________________________/

              |<---------------->|<---------------->|
               Max for device 0    Minimum time is
                is 31 seconds.     0 seconds.
               Max for device 1    No maximum time
                is 30 seconds.     is specified.

Figure 9 - BSY and DRDY timing for software reset



9.3.    PIO data in commands

This class includes:

   *       IDENTIFY DEVICE
   *       READ BUFFER
   *       READ LONG (with and without retry)
   *       READ SECTOR(S) (with and without retry)
   *       READ MULTIPLE

Execution of this class of command includes the transfer of one or more blocks
of data from the device to the host.  The following steps describe the
processing of a PIO data in command.  This description does not include all
possible error conditions.

PIO data in protocol:

a) The host reads the Status or Alternate Status register until BSY bit to
become equal to 0.

b) The host writes the Device/Head register with the appropriate DEV bit value.

c) The host reads the Status or Alternate Status register until the BSY bit is
equal to 0 and the DRDY bit is equal to 1.

d) The host writes any required command parameters to the Features, Sector
Count, Sector Number, Cylinder High, Cylinder Low and Device/Head registers.

e) The host writes the command code to the Command register.

f) The device sets the BSY bit and prepares to execute the command including
preparation to transfer the first block of data to the host.

g) When the block of data is available, the device sets the DRQ bit (setting the
DRQ bit is optional if an error condition exists).  If there is an error
condition, the device sets the appropriate status and error bits as required by
that error condition.  Finally, the device clears the BSY bit and then asserts
INTRQ.

Implementor's Note:  There may be times when the BSY bit is set in step f) and
then cleared in step g) so quickly, that the host may not be able to detect that
the BSY bit had been set.

h) After detecting either BSY bit is equal to 0 by polling the Alternate Status
register or INTRQ, the host reads and saves the contents of the Status register.

i) If the DRQ bit is set, the host transfers a block of data by reading the Data
register.  If any error conditions are present in the status read in step h),
the data transfer may not be valid.

j) In response to the Status register being read, the device negates INTRQ.  In
response to the complete data block being read, one of the following actions is
taken:

- If no error status was presented to the host in step h) and if transfer
of another block is required, the device sets the BSY bit and the above
sequence is repeated from step g).

- If an error status was present in the Status read in step h), the device
clears the DRQ bit and the command execution is complete.

- If the last block was transferred, the device clears the DRQ bit and the
command execution is complete.


The following diagrams the PIO data in steps:

             BSY=1               BSY=1
           +--<---+            +--<---+
           |      | BSY=0      |      | BSY=0               BSY=1
  start ---+-> a -+-------> b -+-> c -+-------> d ---> e,f ------+
                                                                 |
                                                                 |
  +--------------------------------------------------------------+
  |
  |                                          DRQ=0
  |                                        +-->---------+
  |                                        |            |
  |    BSY=1      BSY=0, assert INTRQ      | DRQ=1      |
  +---+------> g ---------------------> h -+-->----> i -+-> j ---+
      |                                                          |
      |   no error and another block, BSY=1                      |
      +------------------<---------------------------------------+
                                                                 |
               error or no more blocks, BSY=0                    |
  +---------------------------<----------------------------------+
  |
  +---> end


9.4.    PIO data out commands

This class includes:

   *   DOWNLOAD MICROCODE
   *   FORMAT TRACK
   *   WRITE BUFFER
   *   WRITE LONG (with and without retry)
   *   WRITE MULTIPLE
   *   WRITE SAME
   *   WRITE SECTOR(S) (with and without retry)
   *   WRITE VERIFY

Execution of this class of command includes the transfer of one or more blocks
of data from the host to the device.  The following steps describe the
processing of a PIO data out command.  This description does not include all
possible error conditions.

PIO data out protocol:

a) The host reads the Status or Alternate Status register until BSY bit is equal
to 0.

b) The host writes the Device/Head register with the appropriate DEV bit value.

c) The host reads the Status or Alternate Status register until BSY bit is equal
to 0 and the DRDY bit is equal to 1.

d) The host writes any required command parameters to the Features, Sector
Count, Sector Number, Cylinder High, Cylinder Low and Device/Head registers.

e) The host writes the command code to the Command register.

f) The device sets the BSY bit and prepares to execute the command including
preparation to receive the first block of data from the host.

g) When ready to receive the first block of data from the host, the device sets
the DRQ bit (setting the DRQ bit is optional if an error condition exists) and
any other status or error bits as required and clears the BSY bit.

Implementor's Note:  There may be times when the BSY bit is set in step f) and
then cleared in step g) so quickly, that the host may not be able to detect that
the BSY bit had been set.

h) The host reads the Status or Alternate Status register until BSY bit is equal
to 0.

i) If the DRQ bit is set, the host transfers a complete block of data to the
device by writing the Data register.

j) Next, one of the following actions is taken:

- If any error status was present in the status read in step h), the
device clears the DRQ bit, asserts INTRQ and the command execution is
complete.  The data transferred in step i) is not processed by the device.

- If no error status was presented to the host in step h), the device sets
the BSY bit and processing continues with the next step.

k) The device processes the data block just received from the host.  When this
processing is completed, one of the following actions is taken:

- If no error occurred while processing the data block and if no
additional blocks are to be transferred, the device clears the BSY bit and
then asserts INTRQ.  Command execution is complete.

- If an error occurred while processing the data block the device sets the
appropriate status and error bits as required by that error condition.
The device clears the BSY bit and then asserts INTRQ.  Command execution
is complete.

- If no error occurred while processing the data block and if transfer of
another block is required, processing continues with the next step.

l) When ready to receive the next data block from the host, the device sets the
DRQ bit, clears the BSY bit and then asserts INTRQ.

m) After detecting either the BSY bit is equal to 0 by polling the Alternate
Status register or INTRQ, the host reads the contents of the Status register.

n) The host transfers a complete block of data to the device by writing the Data
register.

o) The device sets the BSY bit and processing continues at step k).

The following diagrams the PIO data out steps:

             BSY=1               BSY=1
           +--<---+            +--<---+
           |      | BSY=0      |      | BSY=0               BSY=1
  start ---+-> a -+-------> b -+-> c -+-------> d ---> e,f ------+
                                                                 |
                                                                 |
  +--------------------------------------------------------------+
  |
  |                     DRQ=0
  |                   +-->---------+
  |                   |            |
  |        BSY=0      | DRQ=1      |
  +---> g -------> h -+-->----> i -+-> j ---+
                                            |
                                            |
  +-----------------------------------------+
  |
  |  error, DRQ=0, assert INTRQ
  +--->-------------------------> end
  |
  |
  |                   +------------<-------------------------+
  |  no error, BSY=1  |                                      |
  +--->---------------+-> k ---+                             |
                               |                             |
                               |                             |
  +----------------------------+                             |
  |                                                          |
  | no error and no more blocks, BSY=0, assert INTRQ         |
  +--->----------------------------------------------> end   |
  |                                                          |
  |  error, BSY=0, assert INTRQ                              |
  +--->-------------------------> end                        |
  |                                                          |
  | no error and more blocks, BSY=1                          |
  +--->-----------------------------+                        |
                                    |                        |
                                    |                        |
  +---------------------------------+                        |
  |                                                          |
  |        BSY=0/DRQ=1, assert INTRQ             BSY=1       |
  +---> l ---------------------------> m ---> n -------------+


9.5.    Non-data commands

This class includes:

   *   CHECK POWER MODE
   *   DOOR LOCK
   *   DOOR UNLOCK
   *   EXECUTE DEVICE DIAGNOSTIC (DRDY=x)
   *   IDLE
   *   IDLE IMMEDIATE
   *   INITIALIZE DEVICE PARAMETERS (DRDY=x)
   *   MEDIA EJECT
   *   NOP
   *   READ VERIFY SECTOR(S)
   *   RECALIBRATE
   *   SEEK
   *   SET FEATURES
   *   SET MULTIPLE MODE
   *   SLEEP
   *   STANDBY
   *   STANDBY IMMEDIATE

Execution of these commands involves no data transfer.  The following steps
describe the processing of a no data transfer command.  This description does
not include all possible error conditions.  See the EXECUTE DEVICE DIAGNOSTICS
command description in clause 8.8, the NOP command description in clause 8.15
and the SLEEP command description in clause 8.26 for additional protocol
requirements.

a) The host reads the Status or Alternate Status register until the BSY bit is
equal to 0.

b) The host writes the Device/Head register with the appropriate DEV bit value.

c) The host reads the Status or Alternate Status register until the BSY bit is
equal to 0 and the DRDY bit is equal to 1.

d) The host writes any required command parameters to the Features, Sector
Count, Sector Number, Cylinder High, Cylinder Low and Device/Head registers.

e) The host writes the command code to the Command register.

f) The device sets the BSY bit and executes the command.  If any error occurs
while processing the command, the device set the appropriate status and error
bits as required by the error condition.

g) When command processing is completed, the device clears the BSY bit and then
asserts INTRQ.  Command processing is complete.

The following diagrams the no data transfer steps:

             BSY=1               BSY=1
           +--<---+            +--<---+
           |      | BSY=0      |      | BSY=0               BSY=1
  start ---+-> a -+-------> b -+-> c -+-------> d ---> e,f ------+
                                                                 |
                                                                 |
  +--------------------------------------------------------------+
  |
  |        BSY=0
  +---> g -------> end



9.6.    DMA data transfer commands (optional)

This class comprises:

   * READ DMA (with and without retry)
   * WRITE DMA (with and without retry)

Data transfers using DMA commands differ in two ways from PIO transfers:

   * data transfers are performed using the DMA channel

   * A Single interrupt is issued at the completion of the
     command.

Initiation of the DMA transfer commands is identical to the READ SECTOR(S) or
WRITE SECTOR(S) commands except that the host initializes the DMA channel prior
to issuing the command.

The interrupt handler for DMA transfers is different in that no intermediate
sector interrupts are issued on multi-sector commands.

The following steps describe the execution of a DMA command.

a) The host reads the Status or Alternate Status register until the BSY bit is
equal to 0.

b) The host writes the Device/Head register with the appropriate DEV bit value.

c) The host reads the Status or Alternate Status register until the BSY bit is
equal to 0 and the DRDY bit is equal to 1.

d) The host writes any required command parameters to the Features, Sector
Count, Sector Number, Cylinder High, Cylinder Low and Device/Head registers.

e) The host initializes the DMA channel.

Note:  This step may be performed at anytime after step b) and prior to step f).

f) The host writes the command code to the Command register.

g) The device sets the BSY bit and prepares to execute the command.

h) When the device is ready to transfer data, the device asserts DMARQ.  The DMA
data transfer may be split into several partial transfers at the discretion of
the device or DMA channel.  The device shall have either the BSY bit or the DRQ
bit in the status registers during the entire DMA data transfer phase.  If any
error occurs the device set the appropriate status and error bits for the error
condition.  Data transfer is optional if an error condition exists.

i) When the device has completed processing, it clears both the BSY bit and the
DRQ bit and then asserts INTRQ.  Command processing is complete.

j) The host resets the DMA channel

The following diagrams the DMA steps:

             BSY=1               BSY=1
           +--<---+            +--<---+
           |      | BSY=0      |      | BSY=0
  start ---+-> a -+-------> b -+-> c -+-------> d ---> e ---+
                                                            |
                                                            |
  +---------------------------------------------------------+
  |
  |          BSY=1             BSY=0, DRQ=0, assert INTRQ
  +---> f,g -------> h ---> i ----------------------------+
                                                          |
  +-------------------------------------------------------+
  |
  +---> j ---> end


9.7.    Device 0 only configurations

In a single device configuration where device 0 is the only device and the host
selects device 1, device 0 may respond to accesses of the Command Block and
Control Block registers in one of two methods.  These two methods exist because
previous versions of the ATA standard did not specify the required behavior for
this configuration.  The first method is the recommended implementation.

The first method is:

1) A write to the Device Control register shall complete as if device 0 was the
selected device.

2) A write to the Command Block register, other than the Command register, shall
complete as if device 0 was selected.

3) A write to the Command register is ignored.

4) A read of the Control Block or Command Block registers, other than the Status
or Alternate Status registers, shall complete as if device 0 was selected.

5) A read of the Status or Alternate status register returns the value 00H.

Note:  IDX is vendor specific and might change following reset or power mode
changes resulting in other values for status other than 00H.

The second method requires that device 0 implement an Error, Status and
Alternate Status register that is used whenever device 1 is selected.

The second method is:


1) The device 1 Error, Status and Alternate status registers are set to 00H by a
reset.

Note:  IDX is vendor specific and might change following reset or power mode
changes resulting in other values for status other than 00H.

2) A write to the Device Control register shall complete as if device 0 was the
selected device.

3) A write to the Command Block register, other than the Command register, shall
complete as if device 0 was selected.

4) A write to the Command register with a command code other than the INITIALIZE
DEVICE PARAMETERS or EXECUTE DEVICE DIAGNOSTICS command causes the device 1
Error, Status and Alternate status registers to be used as follows:

   a) the BSY bit is set in the device 1 status register.

   b) the ABRT bit is set in the device 1 Error register.

   c) the ERR bit is set in the device 1 status registers.

   d) the BSY bit is cleared in the device 1 status register.

   e) if the nIEN bit in the Device Control Register is cleared,
      the INTRQ signal is asserted.

5) An EXECUTE DEVICE DIAGNOSTIC command is executed as if it addressed to device
0.

6) An INITIALIZE DEVICE PARAMETERS command is executed as if device 1 is present
and is actually executing the command.  The command shall have no effect of the
device parameters of device 0.

7) A read of the Control Block or Command Block registers, other than the Status
or Alternate Status registers, shall complete as if device 0 was selected.

8) A read of the Error, Status or Alternate status register returns the value in
the device 1 copy of these registers.  The device 1 status registers shall
contain 00H following a reset and the value 01H following an attempt to execute
a command, other than EXECUTE DEVICE DIAGNOSTICS or INITIALIZE DEVICE
PARAMETERS, on device 1.



10.     Timing

10.1.   Deskewing

The host shall provide cable deskewing for all signals originating from the
controller.  The device shall provide cable deskewing for all signals
originating at the host.

All timing values and diagrams are shown and measured at the connector of either
device connected to the ATA interface.  No values are given for measurement at
the host interface.

10.2.   Symbols

Certain symbols are used in the timing diagrams.  These symbols and their
respective definitions are listed below.

    / or \    -   signal transition (asserted or negated) *
    < or >    -   data transition (asserted or negated)
    XXXXXX    -   undefined but not necessarily released
    . . .     -   the "other" condition if a signal is shown with no change
    #n        -   used to number the sequence in which events occur e.g. #a, #b
    _ _ __
    __/_ _/   -   a degree of uncertainty as to when a signal may be asserted
    __ _ _
    \_ _\__   -   a degree of uncertainty as to when a signal may be negated

 *   All signals are shown with the asserted condition facing to the top of the
page.  The negated condition is shown towards the bottom of the page relative to
the asserted condition.

10.3.   Terms

The interface uses a mixture of negative and positive signals for control and
data.  The terms asserted and negated are used for consistency and are
independent of electrical characteristics.

In all timing diagrams, the lower line indicates negated, and the upper line
indicates asserted e.g.  the following illustrates the representation of a
signal named TEST going from negated to asserted and back to negated, based on
the polarity of the signal.

                              Assert          Negate
                                   |          |
         Bit Setting=1             |__________|
         Bit Setting=0  TEST  _____/          \_______

                              Assert          Negate
                                   |          |
         Bit Setting=0             |__________|
         Bit Setting=1  TEST- _____/          \_______


10.4.   Data Transfers

The minimum cycle time supported by the device in PIO Mode 3, 4 and Multiword
DMA Mode 1, 2 respectively shall always be greater than or equal to the minimum
cycle time defined by the associated Mode e.g. a drive supporting PIO Mode 4
timing shall not report a value less than 120 nanoseconds, the minimum cycle
time defined for Mode 4 PIO Timings.



10.4.1. PIO Data Transfers

Figure 10 defines the relationships between the interface signals for both 16-bit and 8-bit PIO data transfers.
Peripherals reporting support for PIO Transfer Mode 3 or 4 shall power up in a PIO Transfer Mode 0, 1 or 2.

For PIO modes 3 and above, the minimum value of t0 is specified by word 68 in the Identify Drive parameter list.
The value in word 68 shall not be less than the value shown in the table below.

It is mandatory that IORDY be supported when PIO Mode 3 or 4 are the current mode of operation.


                     |<---------------- t0 --------------------------->|
                     |     _______________________________________________________
 Addr Valid (1)    _______/                                            |          \_____________
                     |    |<----t1---->|                               |<---t9--->|
                     |    |            |<-------- t2 ----------------->|          |<-t8->|
                   __     |            |_______________________________|<----------t2i------>|__
 DIOR-/DIOW-         \_________________/                               \_____________________/
                          |            |                               |                 |
 WRITE (2)                |            |                 _____________________           |
 DD0-15            -------------------------------------<_____________________>-----------------
                          |            |                |<-----t3----->|      |          |
                          |            |                               |<-t4->|          |
 READ (2)                 |            |                  _______________________        |
 DD0-15            --------------------------------------<_______________________XXXX>----------
                          |            |                 |<-----t5---->|         |   |   |
                          |<-t7->|     |                 |             |<--t6--->|   |   |
                          |      |     |                 |             |<----t6Z---->|   |
                          |      |_______________________________________________________|
 IOCS16- (3)       ______________/     |                 |                               \______
                          |            |                 |
                   _______|____________|_________________|______________________________________
 IORDY (4,4-1)            |            |                 |
                          |            |<--tA-->|        |
                   _______|____________|________|________|______________________________________
 IORDY (4,4-2)            \XXXXXXXXXXXXXXXXXXXXX/        |
                          |            |        |        |<-tRD->|
                   _______|____________|________|________|_______|______________________________
 IORDY (4,4-3)            \XXXXXXXXXXXXXXXXXXXXX\________________/
                                                |<------tB------>|

                        FIGURE 10 - PIO Data Transfer to/from Device (Part 1 of 2)

Notes:
(1) Device Address consists of signals CS0-, CS1- and DA2-0
(2) Data consists of DD0-15 (16-bit) or DD0-7 (8-bit)
(3) IOCS16- shown for PIO modes 0,1 and 2.  For other modes, this signal is not valid. (See clause 5.2.11)
(4) The negation of IORDY by the device is used to extend the PIO cycle.  The determination of whether the cycle
is to be extended is made by the host after tA from the assertion of DIOR- or DIOW-.  The assertion and
negation of IORDY are described in the following three cases:
(4-1)  Device never negates IORDY: no wait is generated.
(4-2)  Device starts to drive IORDY low before tA, but causes IORDY to be asserted before tA: no wait
generated.
(4-3)  Device drives IORDY low before tA:  wait generated.  The cycle completes after IORDY is reasserted.
For cycles where a wait is generated and DIOR- is asserted, device shall place read data on DD0-15 for tRD
before causing IORDY to be asserted.

     +------------------------------------------+------+------+------+------+------+-----+
     | PIO                                      |Mode 0|Mode 1|Mode 2|Mode 3|Mode 4|     |
     | timing parameters                        | nsec | nsec | nsec | nsec | nsec |Notes|
+----+------------------------------------------+------+------+------+------+------+-----+
| t0 | Cycle time                         (min) | 600  | 383  | 240  | 180  | 120  | (1) |
| t1 | Address valid to DIOR-/DIOW- setup (min) |  70  |  50  |  30  |  30  |  25  |     |
| t2 | DIOR-/DIOW-      16-bit            (min) | 165  | 125  | 100  |  80  |  70  | (1) |
|    |   Pulse width     8-bit            (min) | 290  | 290  | 290  |  80  |  70  | (1) |
| t2i| DIOR-/DIOW- recovery time          (min) |   -  |   -  |   -  |  70  |  25  | (1) |
| t3 | DIOW- data setup                   (min) |  60  |  45  |  30  |  30  |  20  |     |
| t4 | DIOW- data hold                    (min) |  30  |  20  |  15  |  10  |  10  |     |
| t5 | DIOR- data setup                   (min) |  50  |  35  |  20  |  20  |  20  |     |
| t6 | DIOR- data hold                    (min) |   5  |   5  |   5  |   5  |   5  |     |
| t6Z| DIOR- data tristate                (max) |  30  |  30  |  30  |  30  |  30  | (2) |
| t7 | Addr valid to IOCS16- assertion    (max) |  90  |  50  |  40  | n/a  | n/a  | (4) |
| t8 | Addr valid to IOCS16- released     (max) |  60  |  45  |  30  | n/a  | n/a  | (4) |
| t9 | DIOR-/DIOW- to address valid hold  (min) |  20  |  15  |  10  |  10  |  10  |     |
| tRd| Read Data Valid to IORDY active    (min) |   0  |   0  |   0  |   0  |   0  |     |
|    |  (if IORDY initially low after tA)       |      |      |      |      |      |     |
| tA | IORDY  Setup time                        |  35  |  35  |  35  |  35  |  35  | (3) |
| tB | IORDY  Pulse Width                 (max) |1250  |1250  |1250  |1250  |1250  |     |
+----+------------------------------------------+------+------+------+------+------+-----+
(1) t0 is the minimum total cycle time, t2 is the minimum command active time, and t2i is the minimum command
recovery time or command inactive time.  The actual cycle time equals the sum of the actual command active time
and the actual command inactive time.  The three timing requirements of t0, t2, and t2i shall be met.  The
minimum total cycle time requirements is greater than the sum of t2 and t2i.  This means a host implementation
can lengthen either or both t2 or t2i to ensure that t0 is equal to or greater than the value reported in the
devices identify drive data.  A device implementation shall support any legal host implementation.
(2) This parameter specifies the time from the negation edge of DIOR- to the time that the data bus is no longer
driven by the device (tri-state).
(3) The delay from the activation of DIOR- or DIOW- until the state of IORDY is first sampled.  If IORDY is
inactive then the host shall wait until IORDY is active before the PIO cycle can be completed.  If the device is
not driving IORDY negated at the tA after the activation of DIOR- or DIOW-, then t5 shall be met and tRD is not
applicable.  If the device is driving IORDY negated at the time tA after the activation of DIOR- or DIOW-, then
tRD shall be met and t5 is not applicable.
(4) t7 and t8 apply only to modes 0, 1 and 2.  For other modes, this signal is not valid. (See clause 5.2.11)

               Figure 10 - PIO Data Transfer to/from Device (Part 2 of 2)


10.4.2. Single Word DMA Data Transfer

                    |<----------------------- t0 ----------------------->|
                 ____________                                         _______
 DMARQ       ___/            \_______________________________________/   |
                    |<- tC ->|                                           |
                    |______________________________________________      |___
 DMACK-      _______/                                              \_____/
                    |<--- tI --->|_________________|<----- tJ -----|     |
 DIOR-/DIOW- ____________________/                 \_________________________
                    |            |                 |                     |
                    |            |<------ tD ----->|                     |
 Read               |                      _________________             |
 DD0-15      -----------------------------<_________________>----------------
                    |            |<- tE ->|<- tS ->|<- tF ->|            |
 Write              |                  __________________________        |
 DD0-15     --------------------------<__________________________>-----------
                    |                 |            |             |       |
                    |                 |<--- tG --->|<--  tH   -->|       |

     +----------------------------------------------------------+
     | Single word DMA                  | Mode 0| Mode 1| Mode 2|
     | timing parameters                |  nsec |  nsec |  nsec |
+----+----------------------------------+-------+-------+-------|
| t0 | Cycle time                 (min) |  960  |  480  |  240  |
| tC | DMACK to DMARQ delay       (max) |  200  |  100  |   80  |
| tD | DIOR-/DIOW-      16-bit    (min) |  480  |  240  |  120  |
| tE | DIOR- data access          (max) |  250  |  150  |   60  |
| tF | DIOR- data hold            (min) |    5  |    5  |    5  |
| tG | DIOW- data setup           (min) |  250  |  100  |   35  |
| tH | DIOW- data hold            (min) |   50  |   30  |   20  |
| tI | DMACK to DIOR-/DIOW- setup (min) |    0  |    0  |    0  |
| tJ | DIOR-/DIOW- to DMACK hold  (min) |    0  |    0  |    0  |
| tS | DIOR- setup                (min) | tD-tE | tD-tE | tD-tE |
+---------------------------------------------------------------+
            Figure 11 - Single Word DMA Data Transfer




10.4.3. Multiword DMA Data Transfer

The timings associated with Multiword DMA Transfers are defined below.

For Multiword DMA modes 1 and above, the minimum value of t0 is specified by word 65 in the Identify Drive
parameter list.  The value in word 65 shall not be less than the value shown in the table below.

Devices reporting support for Multiword DMA Transfer Mode 2 shall also support Multiword DMA Transfer Mode 0 and
1 and shall power up with Mode 0 as the default Multiword DMA Mode.

                                  |<----------------- t0 --------------->|
            _________________________________________________________    |               ________
 DMARQ  ___/                                                         \__________________/
                                  |                         |<--tL-->|   |
                                  |                         |            |
               ___________________________________________________________________              _
 DMACK- ______/                                                                   \____________/
              |<-tI->|            |                         |            |
                     |<-- tD ---->|<----------- tK -------->|            |<--tJ-->|
                     |            |                         |            |        |
 DIOR-               |____________|                         |____________|        |
 DIOW-  _____________/            \_________________________/            \_______________________
                     |            |                                              |
                   ->| tE |<-      |                                              |<-tZ->|
 READ                      ________________                            ___________       |
 DD0-15 --------------<XXXX________________XXXXXXXXXXXXXXXXXXXXXXXXXXXX___________XXXXXXX>-------
                          |       |        |
                          |<-tGr->|<--tF-->|
 WRITE                  _____________________                       ____________________
 DD0-15 XXXXXXXXXXXXXXXX_____________________XXXXXXXXXXXXXXXXXXXXXXX____________________XXXXXXXXX
                       |<--tGw--->|<---tH--->|


          Figure 12 - Multiword DMA Data Transfer (Part 1 of 2)


      +----------------------------------------+-----------+-----------+-----+
      | Multiword DMA              |   Mode 0  |   Mode 1  |   Mode 2  |     |
      | timing parameters          |    nsec   |    nsec   |    nsec   |     |
      |                            | Min | Max | Min | Max | Min | Max |Notes|
+-----+----------------------------+-----+-----|-----+-----|-----+-----|-----|
| t0  | Cycle time                 | 480 |     | 150 |     | 120 |     | (1) |
| tC  | DMACK to DMARQ delay       |     | --- |     | --- |     | --- |     |
| tD  | DIOR-/DIOW-      16-bit    | 215 |     |  80 |     |  70 |     | (1) |
| tE  | DIOR- data access          |     | 150 |     |  60 |     | --- |     |
| tF  | DIOR- data hold            |   5 | (2) |   5 |     |   5 |     |     |
| tG  | DIOW- data setup           | 100 |     |  30 |     |  20 | n/a |     |
| tG  | DIOW- data setup           | 100 |     |  30 |     |  20 |     |     |
| tH  | DIOW- data hold            |  20 |     |  15 |     |  10 |     |     |
| tI  | DMACK to DIOR-/DIOW- setup |   0 |     |   0 |     |   0 |     |     |
| tJ  | DIOR-/DIOW- to DMACK hold  |  20 |     |   5 |     |   5 |     |     |
| tKr | DIOR- negated pulse width  |  50 |     |  50 |     |  25 |     | (1) |
| tKw | DIOW- negated pulse width  | 215 |     |  50 |     |  25 |     | (1) |
| tLr | DIOR- to DMARQ delay       |     | 120 |     |  40 |     |  35 |     |
| tLw | DIOW- to DMARQ delay       |     |  40 |     |  40 |     |  35 |     |
| tZ  | DMACK- to tristate         |     |  20 |     |  25 |     |  25 | (2) |
+----------------------------------------------+-----------+-----+-----+-----+
(1) t0 is the minimum total cycle time, tD is the minimum command active time, and tK (tKr or tKw, as
appropriate) is the minimum command recovery time or command inactive time. The actual cycle time equals the sum
of the actual command active time and the actual command inactive time. The three timing requirements of t0, tD,
tK shall be met. The minimum total cycle time requirement, t0, is greater than the sum of tD and tK. This means
a host implementation can lengthen either or both tD or tK to ensure that t0 is equal to the value reported in
the devices identify drive data.. A device implementation shall support any legal host implementation.
(2) The original ATA standard defined a maximum value for tF.  Meaning of this value was not clear. This
parameter has been renamed to tZ and specifies the time from the negation edge of DMACK- to the time the Device
Data signals are no longer driven by the device (tristate). The tZ parameter applies only at the end of a
Multiword DMA cycle, i.e., when DMACK is negated.  The device may actively drive the Device Data signals, or may
tristate the Device Data signals, while DMACK- is active from the first time that DIOR- is asserted until DMACK-
is negated as long as tE and tF requirements are met.

          Figure 12 - Multiword DMA Data Transfer (Part 2 of 2)





10.5.   Power on and hard reset

              ______
 RESET- _____/      \_____________________________________________________
             |<-tM->|
             |      |
             |      |
             |      |          Device 0
          _ _ _ _ _ _ _ _______ _ _ _ _ _ _ _ _ _ _ _ _ _|
 BSY      _ _ _ _ _ _ _/       \_ _ _ _ _ *1  _ _ _ _ _ _\________________
                  ->|tN|<-
          _ _ _ _ _ _ _ _         _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
 DASP-    _ _ _ _ _ _ _ _\_______/_ _ _ _ *2 _ _ _ _ _ _ _ _ _ _\=== *3 ==
                  ->| tP |<-     |                       |_ _ _ __________
 Control Registers_______________________________________/_ _ _ /
                    |  |
                    |  |
                    |  |
                    |  |       Device 1
        _ _ _ _ _ _ _ _ _________________________________|
 BSY    _ _ _ _ _ _ _ _/                                 \________________
         _ _ _ _ _ _ _ _ _ _                              ______ _ _ _ _ _
 PDIAG-  _ _ _ _ _ _ _ _ _ _\____________________________/      \_ _ _ _ _
                    |          |<----------- tQ -------->|
        _ _ _ _ _ _ _ _ _ _ _ _ _________________________ _ _ _
 DASP-  _ _ _ _ _ _ _ _ _ _ _ _/                         \ _ _ _\=== *3 ==
                    |<-  tR  ->|
                    |<-------------------- tS ----------------->|
                                                          _ _ _ __________
 Control Registers_______________________________________/_ _ _ /

*1 Device 0 can set the BSY bit equal to zero if Device 1 not present
*2 Device 0 can use DASP- to indicate it is active if Device 1 is not present
*3 DASP- can be asserted to indicate that the device is active

            +--------------------------------+
            | Label             |   Units    |
            |-------------------+------------|
            | tM         (Min)  |  25   usec |
            | tN         (Max)  | 400   nsec |
            | tP         (Max)  |   1   msec |
            | tQ         (Max)  |  30   secs |
            | tR Device 0(Max)  | 450   msec |
            | tR Device 1(Max)  | 400   msec |
            | tS         (Max)  |  31   secs |
            +--------------------------------+
               Figure 13 - Reset Sequence




Annex A. Diagnostic and reset considerations from a device firmware standpoint

(informative)

A.1. Power on and hardware reset (RESET-)

DASP- is read by Device 0 to determine if Device 1 is present.  If Device 1 is
present Device 0 shall read PDIAG- to determine when it is valid to clear the
BSY bit and whether Device 1 has powered on or reset without error, otherwise
Device 0 clears the BSY bit whenever it is ready to accept commands.  Device 0
may assert DASP- to indicate device activity.

A.2. Software reset

If Device 1 is present Device 0 shall read PDIAG- to determine when it is valid
to clear the BSY bit and whether Device 1 has reset without any errors,
otherwise Device 0 shall simply reset and clear the BSY bit.  DASP- is asserted
by Device 0 (and Device 1 if it is present) in order to indicate device active.

A.3. Device diagnostic command

If Device 1 is present, Device 0 shall read PDIAG- to determine when it is valid
to clear the BSY bit and if Device 1 passed or failed the EXECUTE DEVICE
DIAGNOSTIC command, otherwise Device 0 shall simply execute its diagnostics and
then clear the BSY bit.  DASP- is asserted by Device 0 (and Device 1 if it is
present) in order to
indicate the device is active.

A.4. Truth table

In all the above cases:  Power on, RESET-, software reset, and the EXECUTE
DEVICE DIAGNOSTIC command the Device 0 Error register is calculated as follows:

   +-----------+------------+-----------+-----------+
   |  Device 1 |    PDIAG-  |  Device 0 |  Error    |
   |  Present? |  Asserted? |  Passed   |  Register |
   +-----------+------------+-----------+-----------+
   |    Yes    |    Yes     |    Yes    |    01h    |
   |    Yes    |    Yes     |    No     |    0xh    |
   |    Yes    |    No      |    Yes    |    81h    |
   |    Yes    |    No      |    No     |    8xh    |
   |    No     | (not read) |    Yes    |    01h    |
   |    No     | (not read) |    No     |    0xh    |
   +-----------+------------+-----------+-----------+
Where x indicates the appropriate Diagnostic Code for the
Power on, RESET-, software reset, or device diagnostics error.

               Table 15 - Reset Error register Values





A.5. Power on or hardware reset algorithm

NOTE:  In the following algorithms, the notation 1* refers to the Drive 1 status
register copy that Drive 0 keeps when there is no Drive 1 present.

A.5.1 Algorithm for Device 0

1) Power on or hardware reset is detected by the device's hardware.
2) The hardware should automatically do the following within 400 nsec of the
negation of RESET-:
a) Set up the hardware to report both Device 0 and Device 1* status registers.
b) Set the BSY bit to one in the Device 0 Status register.
c) Set the BSY bit to one in the Device 1* Status register.
3) The device shall determine if it is Device 0 or Device 1.  This can be done
at least two different ways:  by jumper or by using the CSEL signal.
4) Set up PDIAG- and DASP:
a) Set up PDIAG- as an input.
b) Release DASP- and set up DASP- as an input.
c) Monitor DASP- until DASP- is asserted by Device 1 or for 450 msec.
d) If DASP- is asserted within 450 msec, store the fact that Device 1 is
present and set up the hardware so it reports Device 0 status only.
e) If DASP- is not asserted within 450 msec, store the fact that Device 1 is
not present and set up the hardware so it reports both Device 0 and 1* status
registers.
f) Set up DASP- as an output.
g) Assert DASP-.
NOTE:  Steps 2-4 complete within 450 msec of the negation of RESET-.
5) Perform any remaining time critical hardware initialization including
starting the spin up of the device if needed.  Complete all the hardware
initialization and diagnostic tests needed to get the device ready, including:
a) Set the Sector Count register to 01h.
b) Set the Sector Number register to 01h.
c) Set the Cylinder Low register to 00h.
d) Set the Cylinder High register to 00h.
e) Set the Device/Head register to 00h.
6) If Device 1 was detected in step 4:
a) Monitor PDIAG- until PDIAG- is asserted by Device 1 or for 31 seconds.
b) If PDIAG- is asserted within 31 seconds, set bit 7 equal to 0 in the Error
register.
c) If PDIAG- is not asserted within 31 seconds, set bit 7 equal to 1 in the
Error register.
7) Post Device 0's initialization and diagnostic results:
a) If Device 0 completed all initialization and diagnostics without error, set
bits 6-0 of the Error register to 0000001b.
b) If Device 0 failed any initialization or diagnostics, set bits 6-0 of the
Error register to a value other than 0000001b as described in Table 11.
8) Set the BSY bit of the Status register to zero and set Drive 1* Status
register to 00H.
NOTE:  Steps 2-8 complete within 31 seconds.
9) Finish initialization and optionally finish spin up.
10) Post Ready status:
a) Set the DRDY bit to one and the DSC bit to one in the Status register.
b) Negate DASP-.


A.5.2 Algorithm for Device 1

1) Power on or hardware reset is detected by the device's hardware.
2) The hardware should automatically do the following within 400 nsec of the
negation of RESET-:
a) Set up the hardware to report both Device 0 and Device 1* status registers.
b) Set the BSY bit to one in the Device 0 Status register.
c) Set the BSY bit to one in the Device 1* Status register.
3) The device shall determine if it is Device 0 or Device 1.  This can be done
at least two different ways:  by jumper or by using the CSEL signal.
4) Set up PDIAG- and DASP:
a) Negate the PDIAG- signal.
b) Set up PDIAG- as an output.
c) Assert the DASP- signal.
d) Set up DASP- as an output.
e) Set up the hardware to report Device 1 status only.
NOTE:  Steps 2-4 complete within 400 msec of the negation of RESET-.
5) Perform any remaining time critical hardware initialization including
starting the spin up of the device if needed.  Complete all the hardware
initialization and diagnostic tests needed to get the device ready, including:
a) Set the Sector Count register to 01h.
b) Set the Sector Number register to 01h.
c) Set the Cylinder Low register to 00h.
d) Set the Cylinder High register to 00h.
e) Set the Device/Head register to 00h.
6) Post Device 1's initialization and diagnostic results:
a) If Device 1 completed all initialization and diagnostic without error, Set
the Error register to 01h and assert PDIAG-.
b) If Device 1 failed any initialization or diagnostics, set the Error
register to a value other than 01h (see Table 11) and do not assert PDIAG-.
7) Set the status register to 00.
NOTE:  Steps 2-7 complete within 30 seconds.
8) Finish initialization and optionally finish spin up.
9) Post Ready status:
a) Set the DRDY bit to one and, if spin up is also complete, the DSC bit to
one in the Status register.
b) Negate DASP-.
10) If not previously done, wait for spin up to complete and then set the DSC
bit in the Status register to one.
11) Negate DASP- when the Command register is written or after 30 seconds.


A.6 Software Reset Algorithm

A.6.1 Algorithm for Device 0

1) SRST bit set to 1 is detected by the device's hardware.
2) The hardware should set the BSY bit in the Status register to one within 400
nsec of the setting of SRST bit to one.
NOTE:  Steps 1-2 complete within 1 msec.
3) Assert DASP-.
4) Finish all the hardware initialization needed to place the device in reset
including all diagnostics.
5) Wait for SRST bit to be set to 0.
6) Reset the Command Block registers:
a) Set the Sector Count register to 01h.
b) Set the Sector Number register to 01h.
c) Set the Cylinder Low register to 00h.
d) Set the Cylinder High register to 00h.
e) Set the Device/Head register to 00h.
7) If Device 1 is present:
a) Monitor PDIAG- for 31 seconds or until PDIAG- is asserted by Device 1.
b) If PDIAG- is asserted within 31 seconds, set bit 7 to 0 in the Error
register.
c) If PDIAG- is not asserted within 31 seconds, set bit 7 to 1 in the Error
register.
8) Post Device 0's initialization and diagnostic results:
a) If Device 0 completed all initialization and diagnostics without error, set
bits 6-0 of the Error register the value 0000001b.
b) If Device 0 failed any initialization or diagnostics, set bits 6-0 of the
Error register to a value other than 0000001b (see Table 11).
NOTE: Steps 6-8 complete within 31 seconds.
9) Set the DRDY bit in its Status register and set Drive 1* Status register to
00h.

A.6.2 Algorithm for Device 1

1) SRST bit equal to 1 is detected by the device's hardware.
2) The hardware should set 80h in the Status register within 400 nsec.
3) Negate the PDIAG- signal.
NOTE:  Steps 1-3 complete within 1 msec.
4) Assert DASP-.
5) Finish all the hardware initialization needed to place the device in reset
including all diagnostics.
6) Wait for SRST bit to be set to 0.
7) Reset the Command Block registers:
a) Set the Sector Count register to 01h.
b) Set the Sector Number register to 01h.
c) Set the Cylinder Low register to 00h.
d) Set the Cylinder High register to 00h.
e) Set the Device/Head register to 00h.
8) Post Device 1's initialization and diagnostic results:
a) If Device 1 completed all initialization and diagnostics without error, set
bits 6-0 of the Error register the value 01h and assert PDIAG-.
b) If Device 1 failed any initialization or diagnostics, set bits 6-0 of the
Error register to a value other than 01h (see Table 11) and does not assert
PDIAG-.
NOTE: Steps 7-9 complete within 30 seconds.
9) Set the DRDY bit in the Status register when ready to accept any command.



A.7.  Diagnostic Command Algorithm

A.7.1 Algorithm for Device 0

1) The EXECUTE DEVICE DIAGNOSTIC command is received.
2) The hardware should set 80h in the Status register within 400 nsec.
3) The hardware should set 80h in the Device 1* Status register.
NOTE:  Steps 1-3 complete within 1 msec.
4) Assert DASP-.
5) Perform all the device diagnostics and note the results.
6) Finish all the hardware initialization needed to get the device ready to
receive any type of command from the host including:
a) Set the Sector Count register to 01h.
b) Set the Sector Number register to 01h.
c) Set the Cylinder Low register to 00h.
d) Set the Cylinder High register to 00h.
e) Set the Device/Head register to 00h.
7) If Device 1 is present:
a) Monitor PDIAG- until PDIAG- is asserted by Device 1 or for 6 seconds.
b) If PDIAG- is asserted within 6 seconds, set bit 7 to 0 in the Error
register.
c) If PDIAG- is not asserted within 6 seconds, set bit 7 to 1 in the Error
register.
8) Post Device 0's initialization and diagnostic results:
a) If Device 0 completed all initialization and diagnostics without error, set
bits 6-0 of the Error register the value 0000001b.
b) If Device 0 failed any initialization or diagnostics, set bits 6-0 of the
Error register to a value other than 0000001b (see Table 11).
NOTE: Steps 2-8 complete within 6 seconds.
9) Set the Status register to 50h and set Drive 1* Status register to 00h.
10) Assert INTRQ.

A.7.2 Algorithm for Device 1

1) The EXECUTE DEVICE DIAGNOSTIC command is received.
2) The hardware should set 80h in the Status register within 400 nsec.
3) Negate the PDIAG- signal.
NOTE:  Steps 1-3 complete within 1 msec.
4) Assert DASP-.
5) Perform all the device diagnostics and note the results.
6) Finish all the hardware initialization needed to get the device ready to
receive any type of command from the host including:
a) Set the Sector Count register to 01h.
b) Set the Sector Number register to 01h.
c) Set the Cylinder Low register to 00h.
d) Set the Cylinder High register to 00h.
e) Set the Device/Head register to 00h.
7) Post Device 1's initialization and diagnostic results:
a) If Device 1 completed all initialization and diagnostics without error, set
bits 6-0 of the Error register the value 1 and assert PDIAG-.
b) If Device 1 failed any initialization or diagnostics, set bits 6-0 of the
Error register to a value of 2 or greater indicating the type of failure and
do not assert PDIAG-.
NOTE: Steps 2-7 complete within 5 seconds.
8) Set the DRDY bit in the Status register when ready to accept any command.



Annex B. 44-Pin Small Form Factor Connector
(informative)


This annex describes a connector alternative often used for 2 1/2" or smaller
devices.  This alternative was developed by the Small Form Factor (SFF)
Committee, an industry ad hoc group.

In an effort to broaden the applications for small form factor devices, a group
of companies representing system integrators, device suppliers, and component
suppliers decided to address the issues involved.

A primary purpose of the SFF Committee was to define the external dimensions of
small form factor devices so that products from different vendors could be used
in the same mounting configurations.

The restricted area, and the mating of devices directly to a motherboard
required that the number of connectors be reduced, which caused the assignment
of additional pins for power.  Power is provided to the devices on the same
connector as used for the signals, and addresses are set by the receptacle into
which the devices are plugged.

The 50-pin connector that has been widely adopted across industry for SFF
devices is a low density 2mm connector which has no shroud on the plug which is
mounted on the device.  A number of suppliers provide intermatable components.
The following information has been provided to assist users in specifying
components used in an implementation.

       Signals Connector Plug                      DuPont 86451 or equivalent
       Signals Connector Receptacle                DuPont 86455 or equivalent

B.1. 44-pin signal assignments

The signals assigned for 44-pin applications are described in table 16.
Although there are 50 pins in the plug, a 44 pin mating receptacle may be
used(the removal of pins E and F provides room for the wall of the receptacle).

Some devices may utilize pins A, B, C and D for option selection via physical
jumpers.  Such implementations may require use of the 44 pin receptacles.

44-pin signal assignments for ATA

The first four pins of the connector plug located on the device are not to be
connected to the host, as they are reserved for manufacturer's use.  Pins E, F
and 20 are keys, and are removed.

+-------------------------------------------1-E-----+
| o o o o o o o o o o o o o o o o o o o o o o K C A |
| o o o o o o o o o o o o K o o o o o o o o o K D B |
+44----------------------20-----------------2-F-----+

+=================-=========-=============-=========-==================+
|    Signal       |Connector|             |Connector|     Signal       |
|     name        | contact |  Conductor  | contact |      name        |
|-----------------+---------+-------------+---------+------------------|
|  Vendor specific|    A    |             |     B   |  Vendor specific |
|  Vendor specific|    C    |             |     D   |  Vendor specific |
|  (keypin)       |    E    |             |     F   |  (keypin)        |
|  RESET-         |    1    |    1 |  2   |     2   |  Ground          |
|  DD7            |    3    |    3 |  4   |     4   |  DD8             |
|  DD6            |    5    |    5 |  6   |     6   |  DD9             |
|  DD5            |    7    |    7 |  8   |     8   |  DD10            |
|  DD4            |    9    |    9 | 10   |    10   |  DD11            |
|  DD3            |   11    |   11 | 12   |    12   |  DD12            |
|  DD2            |   13    |   13 | 14   |    14   |  DD13            |
|  DD1            |   15    |   15 | 16   |    16   |  DD14            |
|  DD0            |   17    |   17 | 18   |    18   |  DD15            |
|  Ground         |   19    |   19 | 20   |    20   |  (keypin)        |
|  DMARQ          |   21    |   21 | 22   |    22   |  Ground          |
|  DIOW-          |   23    |   23 | 24   |    24   |  Ground          |
|  DIOR-          |   25    |   25 | 26   |    26   |  Ground          |
|  IORDY          |   27    |   27 | 28   |    28   |  SPSYNC:CSEL     |
|  DMACK-         |   29    |   29 | 30   |    30   |  Ground          |
|  INTRQ          |   31    |   31 | 32   |    32   |  IOCS16-         |
|  DA1            |   33    |   33 | 34   |    34   |  PDIAG-          |
|  DAO            |   35    |   35 | 36   |    36   |  DA2             |
|  CS0-           |   37    |   37 | 38   |    38   |  CS1-            |
|  DASP-          |   39    |   39 | 40   |    40   |  Ground          |
|* +5v (Logic)    |   41    |   41 | 42   |    42   |  +5V (Motor)   * |
|* Ground (Return)|   43    |   43 | 44   |    44   |  TYPE- (0=ATA)*  |
|----------------------------------------------------------------------|
|     * Pins which are additional to those of the 40-pin cable.        |
+======================================================================+
                    Table 16 - Signal Assignments for 44-Pin ATA





Annex C. 68-Pin Small Form Factor Connector
(informative)

C.1. Overview

This appendix defines the pinouts used for the 68-pin alternative connector for
the AT Attachment Interface. This connector is the same as the one defined by
PCMCIA.  This appendix defines a pinout alternative that allows a device to
function as an AT Attachment Interface compliant device, while also allowing the
device to be compliant with PC Card-ATA mode defined by PCMCIA.  The signal
protocol allows the device to identify the host interface as being 68-pin ATA or
PCMCIA.

To simplify the implementation of dual-interface devices, the 68-pin AT
Attachment Interface maintains commonality with as many PC Card-ATA signals as
possible, while supporting full command and signal compliance with the ATA
standard.

The 68-pin ATA pinout does not cause damage or loss of data if a PCMCIA card is
accidentally plugged into a host slot supporting this interface.  The inversion
of the reset signal between the ATA and PCMCIA interfaces prevents loss of data
if the device is unable to reconfigure itself to the appropriate host interface.

C.2. Signals

This Specification relies upon the electrical and mechanical characteristics of
PCMCIA and unless otherwise noted, all signals and registers with the same names
as PCMCIA signals and registers have the same meaning as defined in PCMCIA.

The PC Card-ATA specification is used as a reference to identify the signal
protocol used to identify the host interface protocol.

Unless otherwise noted, all signals and registers with the same names as ATA
signals and registers have the same meaning as defined in X3.221-199x, which
defines the protocol by which commands are directed to the storage device.

C.3. Signal Descriptions

Any signals not defined below are as described in the ATA, PCMCIA, or the PC
Card-ATA documents.

Table 17 shows the ATA signals and relationships such as direction, as well as
providing the signal name of the PCMCIA equivalent.

 ===================================== ======================================
 |Pin|Signal |Hst|Dir|Dev|PCMCIA     | |Pin|Signal |Hst|Dir|Dev|PCMCIA      |
 ===================================== ======================================
 |  1|Ground | x  ---> x |Ground     | | 35|Ground | x  ---> x |Ground      |
 |  2|DD3    | x <---> x |D3         | | 36|CD1-   | x <---  x |CD1-        |
 |  3|DD4    | x <---> x |D4         | | 37|DD11   | x <---> x |D11         |
 |  4|DD5    | x <---> x |D5         | | 38|DD12   | x <---> x |D12         |
 |  5|DD6    | x <---> x |D6         | | 39|DD13   | x <---> x |D13         |
 |  6|DD7    | x <---> x |D7         | | 40|DD14   | x <---> x |D14         |
 |  7|CS0-   | x  ---> x |CE1-       | | 41|DD15   | x <---> x |D15         |
 |  8|       |    ---> i |A10        | | 42|CS1-   | x  --->x*1|CE2-        |
 |  9|SELATA-| x  ---> x |OE-        | | 43|       |   <---  i |VS1-        |
 | 10|       |           |           | | 44|DIOR-  | x  ---> x |IORD-       |
 | 11|CS1-   | x  --->x*1|A9         | | 45|DIOW-  | x  ---> x |IOWR-       |
 | 12|       |    ---> i |A8         | | 46|       |           |            |
 | 13|       |           |           | | 47|       |           |            |
 | 14|       |           |           | | 48|       |           |            |
 | 15|       |    ---> i |WE-        | | 49|       |           |            |
 | 16|INTRQ  | x <---  x |READY/IREQ-| | 50|       |           |            |
 | 17|VCC    | x  ---> x |VCC        | | 51|VCC    | x  ---> x |VCC         |
 | 18|       |           |           | | 52|       |           |            |
 | 19|       |           |           | | 53|       |           |            |
 | 20|       |           |           | | 54|       |           |            |
 | 21|       |           |           | | 55|M/S-   | x  --->x*2|            |
 | 22|       |    ---> i |A7         | | 56|CSEL   | x  --->x*2|            |
 | 23|       |    ---> i |A6         | | 57|       |   <---  i |VS2-        |
 | 24|       |    ---> i |A5         | | 58|RESET- | x  ---> x |RESET       |
 | 25|       |    ---> i |A4         | | 59|IORDY  | o <--- x*3|WAIT-       |
 | 26|       |    ---> i |A3         | | 60|DMARQ  | o <--- x*3|INPACK-     |
 | 27|DA2    | x  ---> x |A2         | | 61|DMACK- | o  ---> o |REG-        |
 | 28|DA1    | x  ---> x |A1         | | 62|DASP-  | x <---> x |BVD2/SPKR-  |
 | 29|DA0    | x  ---> x |A0         | | 63|PDIAG- | x <---> x |BVD1/STSCHG-|
 | 30|DD0    | x <---> x |D0         | | 64|DD8    | x <---> x |D8          |
 | 31|DD1    | x <---> x |D1         | | 65|DD9    | x <---> x |D9          |
 | 32|DD2    | x <---> x |D2         | | 66|DD10   | x <---> x |D10         |
 | 33|IOCS16-| x <---  x |WP/IOIS16- | | 67|CD2-   | x <---  x |CD2-        |
 | 34|Ground | x  ---> x |Ground     | | 68|Ground | x  ---> x |Ground      |
 ===================================== ======================================
                Table 17 - Signal Assignments for 68-Pin ATA


The Dir column indicates the direction of the signal between host and device.
An x in the Hst column means this signal shall be supported by the Host.  An x
in the Dev column means this signal shall be supported by the device.  An i in
the Dev column means this signal shall be ignored by the device while in 68-pin
ATA mode.  An o means this signal is Optional. If there is nothing in Dev column
for a pin location, then no connection should be made to that pin.

NOTES:
 *1 The device shall support only one CS1- signal pin.
 *2 The device shall support either M/S- or CSEL but not both.
 *3 The device shall hold this signal negated if it does not
    support the function.

C.3.1. CD1- (Card Detect 1)

This signal shall be grounded by the device. CD1- and CD2- are used by the host
to detect the presence of the device.

C.3.2. CD2- (Card Detect 2)

This signal shall be grounded by the device. CD1- and CD2- are used by the host
to detect the presence of the device.

C.3.3. CS1- (Device chip Select 1)

Hosts shall provide CS1- on both the pins identified in Table 17.

Devices are required to recognize only one of the two pins as CS1-.

C.3.4. DMACK- (DMA Acknowledge)

This signal is optional for hosts.

This signal is optional for devices.

If this signal is supported by the host or the device, the function of DMARQ
shall also be supported.

C.3.5. DMARQ (DMA Request)

This signal is optional for hosts.

If this signal is supported by the host or the device, the function of DMACK-
shall also be supported.

C.3.6. IORDY (I/O Channel Ready)

This signal is optional for hosts.

C.3.7. M/S- (Master/Slave)

This signal is the inverted form of CSEL. Hosts shall support both M/S- and CSEL
though devices need only support one or the other.

Hosts shall assert CSEL and M/S- prior to applying VCC to the connector.

C.3.8. SELATA- (Select 68-pin ATA)

This pin is used by the host to select which mode to use, PC Card-ATA mode or
the 68-pin ATA mode. To select 68-pin ATA mode, the host shall assert SELATA-
prior to applying power to the connector, and shall hold SELATA- asserted.

The device shall not re-sample SELATA- as a result of either a Hard or Soft
Reset. The device shall ignore all interface signals for 19 msec after the host
supplies Vcc within the device's voltage tolerance. If SELATA- is negated
following this time, the device shall either configure itself for PC Card-ATA
mode or not respond to further inputs from the host.

C.4. Removability Considerations

This Specification supports the removability of devices which use the ATA
protocol. As removability is a new consideration for ATA devices, several issues
need to be considered with regard to the insertion or removal of devices.

C.4.1. Device Recommendations

The following are recommendations to device implementors:

*       CS0-, CS1-, RESET- and SELATA- should be negated on the device to
prevent false selection during hot insertion.

*       Ignore all interface signals except SELATA- until 19 msec after the host
supplies VCC within the device's voltage tolerance. This time is
necessary to de-bounce the device's power on reset sequence. Once in the
68-pin ATA mode, if SELATA- is ever negated following the 19 msec de-
bounce delay time, the device should disable itself until VCC is
removed.

- The DOOR LOCK and DOOR UNLOCK commands and the MC and MCR bits in the
Error register should be used to prevent unexpected removal of the
device or media.

C.4.2. Host Recommendations

The following are recommendations to host implementors:

*       Connector pin sequencing should protect the device by making contact to
ground before any other signal in the system.

*       SELATA- should be asserted at all times.

*       All devices should be reset and reconfigured to the same base address
each time a device at that address is inserted or removed.

*       The removal or insertion of a device at the same address should be
detected so as to prevent the corruption of a command.

- The DOOR LOCK and DOOR UNLOCK commands and the MC and MCR bits in the
Error register should be used to prevent unexpected removal of the
device or media.


Annex D.  Identify Device Data For ATA Devices Below 8 GB

D. Identify Drive Data Requirements

D.1 Definitions and Background Information

The following abbreviations are used in this annex:

- 528 MB is used to describe a drive that has 1,032,192 sectors
         or 528,482,304 bytes.

- 8 GB is used to describe a drive that has 16,515,072 sectors
         or 8,455,716,864 bytes.

The original IBM PC BIOS (Basic Input/Output System) imposed
several restrictions on the support of disk drives, and these
have been incorporated into many higher level software products.
One such restriction limits the capacity of a hard disk drive.
Most BIOS software cannot support a disk drive with more than
1,024 cylinders, 16 heads and 63 sectors per track.  The maximum
addressable capacity of an ATA disk drive under this scheme is
528 MB.

There is growing support of auto-configuration for disk drives on
PC systems.  The auto-configuration capability usually resides in
the BIOS and uses the Identify Drive command data to configure an
ATA disk drive.

This annex defines rules for the Identify Drive data of
all capacity ATA disk drives and allows BIOS support of ATA
drives up to 8 GB using Cylinder/Head/Sector (CHS) addressing.

This specification defines information that newer BIOSs and
system software can use to determine the true size of a disk
drive and access the full capacity of the drive.

D.2 Cylinder, Head and Sector Addressing

BIOSs and other software that operate an ATA disk drive in CHS
(Cylinder, Head and Sector) addressing mode use Identify Drive
data words 1, 3, 6 and words 53-58 to ascertain the appropriate
translation mode to use and determine the capacity of an ATA disk
drive.

Maximum compatibility is achieved if the following rules are
obeyed.  These rules limit the values placed into words 1, 3, 6,
and 53-58.  The rules specified here for CHS addressing apply to
drives up to 8 GB.

D.2.1.  Word 1

For drives less than or equal to 528 MB, Identify Data word 1
(Default Cylinders) shall not specify a value greater than 1,024.

If a drive is greater than 528 MB but less than or equal to 8 GB,
the maximum value that shall be placed into this word is determined
by the value in Word 3 as shown in the following table.

   Value in Word 3      Maximum value in Word 1

       1  1h                 65,535 FFFFh
       2  2h                 65,535 FFFFh
       3  3h                 65,535 FFFFh
       4  4h                 65,535 FFFFh
       5  5h                 32,767 7FFFh
       6  6h                 32,767 7FFFh
       7  7h                 32,767 7FFFh
       8  8h                 32,767 7FFFh
       9  9h                 16,383 3FFFh
      10  Ah                 16,383 3FFFh
      11  Bh                 16,383 3FFFh
      12  Ch                 16,383 3FFFh
      13  Dh                 16,383 3FFFh
      14  Eh                 16,383 3FFFh
      15  Fh                 16,383 3FFFh
      16 10h                 16,383 3FFFh

The value in this word shall not change.

D.2.2.  Word 3

Identify Data word 3 (Default Heads) shall not specify a value
greater than 16.

The value in this word shall not change.

D.2.3 Word 6

For drives of 8 GB or less, Identify Data word 6 (Default
Sectors) shall not specify a value greater than 63.

The value in this word shall not change.

D.2.4 Use of words 53 through 58

ATA drives that are over 528 MB shall implement words 53-58.
Drives not over 528 MB may also implement these words.  These
words define the addressing for all sectors accessible in CHS
mode.

D.2.5 Word 53

Identify Data word 53 bit 0 shall be set to 1 at all times that
the drive is in a valid translation mode.  Some drives may have
translation modes that cannot be supported.  An attempt to put a
drive into one of these unsupported modes shall cause word 53 bit
0 to be set to 0 with words 54-58 cleared to zero until a valid
translation mode is established.

D.2.6 Word 54

Identify Data word 54 (Current Cylinders) shall specify the
number of full logical cylinders that can be accessed in the
current translation mode.  If an Initialize Drive Parameters
command has not been executed, the contents of this word shall be
the same as word 1. If an Initialize Drive Parameters command has
been executed, this word is the integer result of dividing the
total number of user sectors (this value may be in words 60-61)
by the number of sectors per logical cylinder ( [word55] x
[word56] ), but shall not be a value greater than 65,535.

D.2.7 Word 55

Identify Data word 55 (Current Heads) is the number of heads
specified by the last Initialize Drive Parameters command.  This
word may contain a value of between 1 and 16.  If an Initialize
Drive Parameters command has not been executed, the contents of
this word shall be the same as word 3.

D.2.8 Word 56

Identify Data word 56 (Current Sectors) is the number of sectors
specified by the last Initialize Drive Parameters command.  This
word may contain a value of between 1 and 255.  If an Initialize
Drive Parameters command has not been executed, the contents of
this word shall be the same as word 6.

D.2.9 Words 57-58

Identify Data words 57-58 contain a 32-bit value that shall be
equal to [word54] x [word55] x [word56].  If words 60-61, LBA
sectors, are not zero, words 57-58 shall be less than or equal to
the value in words 60-61 at all times.


D.3 Logical Block Addressing

It is recommended that ATA drives over 528 MB support Logical
Block Addressing (LBA).

D.3.1 Words 60-61

Identify Data words 60-61 shall specify the total number of user
sectors available in LBA mode at all times.  This value shall be
equal to or greater than the value in words 57-58 at all times.
The contents of these words shall not change.

D.3.2 Orphan Sectors

The sectors, if any, between the last sector addressable in CHS
mode and the last sector addressable in LBA mode are known as
"orphan" sectors.  A drive may or may not allow access to these
sectors in CHS addressing mode.

The values in words 1, 3 and 6 should be selected such that the
number of orphan sectors is minimized.  Normally, the number of
orphan sectors should not exceed ( [word55] x [word56] - 1 ).
However, the host system can create conditions where there are a
larger number of orphans sectors by issuing the Initialize Drive
Parameters command with values other than the values in words 3
and 6.


Annex E. ATA Command Set Summary
(informative)

The following two tables are provided to facilitate the understanding of the ATA
command set.  Table 18 provide information on which command codes are currently
defined.  Table 19 provides a list of all of the ATA commands in order of
command code.


     +------------+------------+------------+------------+
     | x0 x1 x2 x3| x4 x5 x6 x7| x8 x9 xA xB| xC xD xE xF|
+----+------------+------------+------------+------------+
| 0x | C  R  R  R | R  R  R  R | R  R  R  R | R  R  R  R |
| 1x | C  *  *  * | *  *  *  * | *  *  *  * | *  *  *  * |
| 2x | C  C  C  C | R  R  R  R | R  R  R  R | R  R  R  R |
| 3x | C  C  C  C | R  R  R  R | R  R  R  R | C  R  R  R |
+----+------------+------------+------------+------------+
| 4x | C  C  R  R | R  R  R  R | R  R  R  R | R  R  R  R |
| 5x | C  R  R  R | R  R  R  R | R  R  R  R | R  R  R  R |
| 6x | R  R  R  R | R  R  R  R | R  R  R  R | R  R  R  R |
| 7x | C  *  *  * | *  *  *  * | *  *  *  * | *  *  *  * |
+----+------------+------------+------------+------------+
| 8x | V  V  V  V | V  V  V  V | V  V  V  V | V  V  V  V |
| 9x | C  C  C  R | C  C  C  C | C  C  V  R | R  R  R  R |
| Ax | R  R  R  R | R  R  R  R | R  R  R  R | R  R  R  R |
| Bx | R  R  R  R | R  R  R  R | R  R  R  R | R  R  R  R |
+----+------------+------------+------------+------------+
| Cx | V  V  V  V | C  C  C  R | C  C  C  C | R  R  R  R |
| Dx | R  R  R  R | R  R  R  R | R  R  R  C | C  C  C  C |
| Ex | C  C  C  C | C  C  C  R | C  C  R  R | C  C  R  C |
| Fx | V  V  V  V | V  V  V  V | V  V  V  V | V  V  V  V |
+----+------------+------------+------------+------------+
Notes:
* - Values 11h through 1Fh are identical to command 10h
    Values 71h through 7Fh are identical to command 70h
C - a unique command
R - Reserved, undefined in current specifications
V - Vender Unique commands
Table 18 - Command Matrix


+------------------------------------+--------------+
| Command Name                       | Command Code |
+------------------------------------+--------------+
| NOP                                |      00h     |
| Reserved                           |    01h-0Fh   |
| RECALIBRATE                        |      1xh     |
| READ SECTOR(S) (w/retry)           |      20h     |
| READ SECTOR(S) (w/o retry)         |      21h     |
| READ LONG (w/retry)                |      22h     |
| READ LONG (w/o retry)              |      23h     |
| Reserved                           |    24h-2Fh   |
| WRITE SECTOR(S) (w/retry)          |      30h     |
| WRITE SECTOR(S) (w/o retry)        |      31h     |
| WRITE LONG (w/retry)               |      32h     |
| WRITE LONG (w/o retry)             |      33h     |
| Reserved                           |    34h-3Bh   |
| WRITE VERIFY                       |      3Ch     |
| Reserved                           |    3Dh-3Fh   |
| READ VERIFY SECTOR(S) (w/retry)    |      40h     |
| READ VERIFY SECTOR(S) (w/o retry)  |      41h     |
| Reserved                           |    42h-4Fh   |
| FORMAT TRACK                       |      50h     |
| Reserved                           |    51h-5Fh   |
| Reserved                           |    60h-6Fh   |
| SEEK                               |      7xh     |
| Vendor specific                    |      8xh     |
| EXECUTE DEVICE DIAGNOSTIC          |      90h     |
| INITIALIZE DEVICE PARAMETERS       |      91h     |
| DOWNLOAD MICROCODE                 |      92h     |
| Reserved                           |      93h     |
| STANDBY IMMEDIATE                  |    94h E0h   |
| IDLE IMMEDIATE                     |    95h E1h   |
| STANDBY                            |    96h E2h   |
| IDLE                               |    97h E3h   |
| CHECK POWER MODE                   |    98h E5h   |
| SLEEP                              |    99h E6h   |
| Vendor specific                    |      9Ah     |
| Reserved                           |    9Bh-9Fh   |
| Reserved                           |    A0h-AFh   |
| Reserved                           |    B0h-BFh   |
| Vendor specific                    |     C0-C3h   |
+------------------------------------+--------------+
Some commands have two command codes and appear in this table twice, once
for each command code.
Table 19 - Commands Sorted By Command Value (Part 1 of 2)

+------------------------------------+--------------+
| Command Name                       | Command Code |
+------------------------------------+--------------+
| READ MULTIPLE                      |      C4h     |
| WRITE MULTIPLE                     |      C5h     |
| SET MULTIPLE MODE                  |      C6h     |
| Reserved                           |      C7h     |
| READ DMA (w/retry)                 |      C8h     |
| READ DMA (w/o retry)               |      C9h     |
| WRITE DMA (w/retry)                |      CAh     |
| WRITE DMA (w/o retry)              |      CBh     |
| Reserved                           |    CCh-CFh   |
| Reserved                           |    D0h-DAh   |
| ACKNOWLEDGE MEDIA CHANGE           |      DBh     |
| BOOT - POST-BOOT                   |      DCh     |
| BOOT - PRE-BOOT                    |      DDh     |
| DOOR LOCK                          |      DEh     |
| DOOR UNLOCK                        |      DFh     |
| STANDBY IMMEDIATE                  |    94h E0h   |
| IDLE IMMEDIATE                     |    95h E1h   |
| STANDBY                            |    96h E2h   |
| IDLE                               |    97h E3h   |
| READ BUFFER                        |      E4h     |
| CHECK POWER MODE                   |    98h E5h   |
| SLEEP                              |    99h E6h   |
| Reserved                           |      E7h     |
| WRITE BUFFER                       |      E8h     |
| WRITE SAME                         |      E9h     |
| Reserved                           |    EAh-EBh   |
| IDENTIFY DEVICE                    |      ECh     |
| MEDIA EJECT                        |      EDh     |
| Reserved                           |      EEh     |
| SET FEATURES                       |      EFh     |
| Vendor specific                    |    F0h-FFh   |
+------------------------------------+--------------+
Some commands have two command codes and appear in this table twice, once
for each command code.
Table 19 - Commands Sorted By Command Value (Part 2 of 2)