c64mem_sta.txt

- C64 RAM Map (STA)
-
- Joe Forster/STA:
- Commodore 64 memory map
- http://sta.c64.org/cbm64mem.html
-
- edited by awsm.de // @awsm9000
- http://www.awsm.de/mem64/
-
- Corrections (typos as well as content), translations etc.
- welcome at: https://github.com/mist64/c64ref
-
------------------------------------------------------------
-
# This plain text file is formatted so that it can be automatically
# parsed in order to create cross-references etc.
# * Lines starting with "-" is top-level information. The first line
#   is the title. Lines starting with "--" are separators.
# * Lines starting with "#" are internal comments.
# * Hex addresses start at column 0.
# * Symbols start at column 13.
# * The description starts at column 21.
# * All lines of the description until the first blank line are
#   combined into the heading.
# * A '.' character at the end of a heading line represents a hard
#   line break.
# * The remaining text is in MarkDown format.
# * All addresses are 4 digits and have a leading '$'.
# The encoding is UTF-8.

$0000        D6510   Processor port data direction register

                     Bits:

                     * Bit #x: 0 = Bit #x in processor port can only be read; 1 = Bit #x in processor port can be read and written.

                     Default: $2F, %00101111.

$0001        R6510   Processor port

                     Bits:

                     * Bits #0-#2: Configuration for memory areas $A000-$BFFF, $D000-$DFFF and $E000-$FFFF. Values:
                     * %x00: RAM visible in all three areas.
                         * %x01: RAM visible at $A000-$BFFF and $E000-$FFFF.
                         * %x10: RAM visible at $A000-$BFFF; KERNAL ROM visible at $E000-$FFFF.
                         * %x11: BASIC ROM visible at $A000-$BFFF; KERNAL ROM visible at $E000-$FFFF.
                         * %0xx: Character ROM visible at $D000-$DFFF. (Except for the value %000, see above.)
                         * %1xx: I/O area visible at $D000-$DFFF. (Except for the value %100, see above.)
                     * Bit #3: Datasette output signal level.
                     * Bit #4: Datasette button status; 0 = One or more of PLAY, RECORD, F.FWD or REW pressed; 1 = No button is pressed.
                     * Bit #5: Datasette motor control; 0 = On; 1 = Off.

                     Default: $37, %00110111.

$0002                Unused

$0003-$0004  ADRAY1  Unused.

                     Default: $B1AA, execution address of routine converting floating point to integer.

$0005-$0006  ADRAY2  Unused.

                     Default: $B391, execution address of routine converting integer to floating point.

$0007        CHARAC  Byte being searched for during various operations.
                     Current digit of number being input.

$0007        INTEGR  Low byte of first integer operand during AND and OR.
                     Low byte of integer-format FAC during INT().

$0008        ENDCHR  Byte being search for during various operations.
                     Current byte of BASIC line during tokenization.
                     High byte of first integer operand during AND and OR.

$0009        TRMPOS  Current column number during SPC() and TAB().

$000A        VERCK   LOAD/VERIFY switch

                     Values:

                     * $00: LOAD.
                     * $01-$FF: VERIFY.

$000B        COUNT   Current token during tokenization.
                     Length of BASIC line during insertion of line.
                     AND/OR switch; $00 = AND; $FF = OR.
                     Number of dimensions during array operations.

$000C        DIMFLG  Switch for array operations

                     Values:

                     * $00: Operation was not called by DIM.
                     * $40-$7F: Operation was called by DIM.

$000D        VALTYP  Current expression type

                     Values:

                     * $00: Numerical.
                     * $FF: String.

$000E        INTFLG  Current numerical expression type

                     Bits:

                     * Bit #7: 0 = Floating point; 1 = Integer.

$000F        GARBFL  Garbage collection indicator during memory allocation for string variable; $00-$7F = There was no garbage collection yet; $80 = Garbage collection already took place.

$000F        DORES   Quotation mode switch during tokenization; Bit #6: 0 = Normal mode; 1 = Quotation mode.
                     Quotation mode switch during LIST; $01 = Normal mode; $FE = Quotation mode.

$0010        SUBFLG  Switch during fetch of variable name

                     Values:

                     * $00: Integer variables are accepted.
                     * $01-$FF: Integer variables are not accepted.

$0011        INPFLG  GET/INPUT/READ switch

                     Values:

                     * $00: INPUT.
                     * $40: GET.
                     * $98: READ.

$0012        TANSGN  Sign during SIN() and TAN()

                     Values:

                     * $00: Positive.
                     * $FF: Negative.

$0013        CHANNL  Current I/O device number.

                     Default: $00, keyboard for input and screen for output.

$0014-$0015  LINNUM  Line number during GOSUB, GOTO and RUN.
                     Second line number during LIST.

$0014-$0015  POKER   Memory address during PEEK, POKE, SYS and WAIT.

$0016        TEMPPT  Pointer to next expression in string stack

                     Values: $19; $1C; $1F; $22.

                     Default: $19.

$0017-$0018  LASTPT  Pointer to previous expression in string stack.

$0019-$0021  TEMPST  String stack, temporary area for processing string expressions (9 bytes, 3 entries).

$0022-$0025  INDEX   Temporary area for various operations (4 bytes).

$0026-$002A  RES     Auxiliary arithmetical register for division and multiplication (4 bytes).

$002B-$002C  TXTTAB  Pointer to beginning of BASIC area.

                     Default: $0801, 2049.

$002D-$002E  VARTAB  Pointer to beginning of variable area.

                     (End of program plus 1.)

$002F-$0030  ARYTAB  Pointer to beginning of array variable area.

$0031-$0032  STREND  Pointer to end of array variable area.

$0033-$0034  FRETOP  Pointer to beginning of string variable area.

                     (Grows downwards from end of BASIC area.)

$0035-$0036  FRESPC  Pointer to memory allocated for current string variable.

$0037-$0038  MEMSIZ  Pointer to end of BASIC area.

                     Default: $A000, 40960.

$0039-$003A  CURLIN  Current BASIC line number

                     Values:

                     * $0000-$F9FF, 0-63999: Line number.
                     * $FF00-$FFFF: Direct mode, no BASIC program is being executed.

$003B-$003C  OLDLIN  Current BASIC line number for CONT.

$003D-$003E  OLDTXT  Pointer to next BASIC instruction for CONT

                     Values:

                     * $0000-$00FF: CONT'ing is not possible.
                     * $0100-$FFFF: Pointer to next BASIC instruction.

$003F-$0040  DATLIN  BASIC line number of current DATA item for READ.

$0041-$0042  DATPTR  Pointer to next DATA item for READ.

$0043-$0044  INPPTR  Pointer to input result during GET, INPUT and READ.

$0045-$0046  VARNAM  Name and type of current variable

                     Bits:

                     * $0045 bits #0-#6: First character of variable name.
                     * $0046 bits #0-#6: Second character of variable name; $00 = Variable name consists of only one character.
                     * $0045 bit #7 and $0046 bit #7:
                         * %00: Floating-point variable.
                         * %01: String variable.
                         * %10: FN function, created with DEF FN.
                         * %11: Integer variable.

$0047-$0048  VARPNT  Pointer to value of current variable or FN function.

$0049-$004A  FORPNT  Pointer to value of current variable during LET.

$0049        ANDMSK  Value of second parameter during WAIT.
                     Logical number during CLOSE and CLOSE
                     Device number of LOAD, SAVE and VERIFY.

$004A        EORMSK  Value of third parameter during WAIT.
                     Device number during OPEN.

$004B-$004C  VARTXT  Temporary area for saving original pointer to current BASIC instruction during GET, INPUT and READ.

$004D        OPMASK  Comparison operator indicator

                     Bits:

                     * Bit #1: 1 = ">" (greater than) is present in expression.
                     * Bit #2: 1 = "=" (equal to) is present in expression.
                     * Bit #3: 1 = "<" (less than) is present in expression.

$004E-$004F          Pointer to current FN function.

$0050-$0052  DSCPNT  Pointer to current string variable during memory allocation.

$0053        FOUR6   Step size of garbage collection

                     Values: $03; $07.

$0054-$0056  JMPER   JMP ABS machine instruction, jump to current BASIC function.

$0055-$0056          Execution address of current BASIC function.

$0057-$005B  TEMPF1  Arithmetic register #3 (5 bytes).

$005C-$0060  TEMPF2  Arithmetic register #4 (5 bytes).

$0061-$0066  FAC     FAC, arithmetic register #1 (5 bytes).

$0066        FACSGN  Sign of FAC

                     Bits:

                     * Bit #7: 0 = Positive; 1 = Negative.

$0067        SGNFLG  Number of degrees during polynomial evaluation.

$0068        BITS    Temporary area for various operations.

$0069-$006E          ARG, arithmetic register #2 (5 bytes).

$006E        ARGSGN  Sign of ARG

                     Bits:

                     * Bit #7: 0 = Positive; 1 = Negative.

$006F-$0070  STRNG1  Pointer to first string expression during string comparison.

$0071-$0072  STRNG2  Temporary area for saving original pointer to current BASIC instruction during VAL().
 
$0071-$0072  POLYPT  Pointer to current item of polynomial table during polynomial evaluation.

$0071-$0072  CURTOL  Auxiliary pointer during array operations.

$0073-$008A  CHRGET  CHRGET. Machine code routine to read next byte from BASIC program or direct command (24 bytes).

$0079        CHRGOT  CHRGOT. Read current byte from BASIC program or direct command.

        007A-$007B   Pointer to current byte in BASIC program or direct command.

$008B-$008F  RNDX    Previous result of RND().

$0090        STATUS  Value of ST variable, device status for serial bus and datasette input/output

                     Serial bus bits:

                     * Bit #0: Transfer direction during which the timeout occured; 0 = Input; 1 = Output.
                     * Bit #1: 1 = Timeout occurred.
                     * Bit #4: 1 = VERIFY error occurred (only during VERIFY), the file read from the device did not match that in the memory.
                     * Bit #6: 1 = End of file has been reached.
                     * Bit #7: 1 = Device is not present.

                     Datasette bits:

                     * Bit #2: 1 = Block is too short (shorter than 192 bytes).
                     * Bit #3: 1 = Block is too long (longer than 192 bytes).
                     * Bit #4: 1 = Not all bytes read with error during pass 1 could be corrected during pass 2, or a VERIFY error occurred, the file read from the device did not match that in the memory.
                     * Bit #5: 1 = Checksum error occurred.
                     * Bit #6: 1 = End of file has been reached (only during reading data files).

$0091        STKEY   Stop key indicator

                     Values:

                     * $7F: Stop key is pressed.
                     * $FF: Stop key is not pressed.

$0092        SVXT    Unknown. (Timing constant during datasette input.)

$0093        VERCK   LOAD/VERIFY switch

                     Values:

                     * $00: LOAD.
                     * $01-$FF: VERIFY.

$0094        C3P0    Serial bus output cache status

                     Bits:

                     * Bit #7: 1 = Output cache dirty, must transfer cache contents upon next output to serial bus.

$0095        BSOUR   Serial bus output cache, previous byte to be sent to serial bus.

$0096        SYNO    Unknown. (End of tape indicator during datasette input/output.)

$0097        XSAV    Temporary area for saving original value of Y register during input from RS232.
                     Temporary area for saving original value of X register during input from datasette.

$0098        LDTND   Number of files currently open

                     Values: $00-$0A, 0-10.

$0099        DFLTN   Current input device number.

                     Default: $00, keyboard.

$009A        DFLTO   Current output device number.

                     Default: $03, screen.

$009B        PRTY    Unknown. (Parity bit during datasette input/output.)

$009C        DPSW    Unknown. (Byte ready indicator during datasette input/output.)

$009D        MSGFLG  System error display switch

                     Bits:

                     * Bit #6: 0 = Suppress I/O error messages; 1 = Display them.
                     * Bit #7: 0 = Suppress system messages; 1 = Display them.

$009E        PTR1    Error counter during LOAD from datasette.

                     Values: $00-$3E, 0-62.

$009E        T1      Block header type during datasette input/output.
                     Length of file name during datasette input/output.
                     Byte to be put into output buffer during RS232 and datasette output.

$009F        PTR2    Error correction counter during LOAD from datasette.

                     Values: $00-$3E, 0-62.

$009F        T2      Auxiliary counter for writing file name into datasette buffer.
                     Auxiliary counter for comparing requested file name with file name read from datasette during datasette input.

$00A0-$00A2  TIME    Value of TI variable, time of day, increased by 1 every 1/60 second (on PAL machines)

                     Values: $000000-$4F19FF, 0-518399 (on PAL machines).
                     
$00A3        R2D2    EOI switch during serial bus output

                     Bits:

                     * Bit #7: 0 = Send byte right after handshake; 1 = Do EOI delay first.

                     Bit counter during datasette output.

$00A4        FIRT    Byte buffer during serial bus input.
                     Parity during datasette input/output.

$00A5        CNTDN   Bit counter during serial bus input/output.
                     Counter for sync mark during datasette output.

$00A6        BUFPT   Offset of current byte in datasette buffer.

$00A7        INBIT   Bit buffer during RS232 input.

$00A8        BITCI   Bit counter during RS232 input.

$00A9        RINONE  Stop bit switch during RS232 input

                     Values:

                     * $00: Data bit.
                     * $01-$FF: Stop bit.

$00AA        RIDATA  Byte buffer during RS232 input.

$00AB        RIPRTY  Parity during RS232 input.
                     Computed block checksum during datasette input.

$00AC-$00AD          Start address for SAVE to serial bus.
                     Pointer to current byte during SAVE to serial bus or datasette.
                     Pointer to line in screen memory to be scrolled during scrolling the screen.

$00AE-$00AF          Load address read from input file and pointer to current byte during LOAD/VERIFY from serial bus.
                     End address after LOAD/VERIFY from serial bus or datasette.
                     End address for SAVE to serial bus or datasette.
                     Pointer to line in Color RAM to be scrolled during scrolling the screen.

$00B0-$00B1          Unknown.

$00B2-$00B3  TAPE1   Pointer to datasette buffer.

                     Default: $033C, 828.

$00B4        BITTS   Bit counter and stop bit switch during RS232 output

                     Bits:

                     * Bits #0-#6: Bit count.
                     * Bit #7: 0 = Data bit; 1 = Stop bit.

                     Bit counter during datasette input/output.

$00B5        NXTBIT  Bit buffer (in bit #2) during RS232 output.

$00B6        RODATA  Byte buffer during RS232 output.

$00B7        FNLEN   Length of file name or disk command; first parameter of LOAD, SAVE and VERIFY or fourth parameter of OPEN

                     Values:

                     * $00: No parameter.
                     * $01-$FF: Parameter length.

$00B8        LA      Logical number of current file.

$00B9        SA      Secondary address of current file.

$00BA        FA      Device number of current file.

$00BB-$00BC  FNADR   Pointer to current file name or disk command; first parameter of LOAD, SAVE and VERIFY or fourth parameter of OPEN.

$00BD        ROPRTY  Parity during RS232 output.
                     Byte buffer during datasette input/output.

$00BE        FSBLK   Block counter during datasette input/output.

$00BF        MYCH    Unknown.

$00C0        CAS1    Datasette motor switch

                     Values:

                     * $00: No button was pressed, motor has been switched off. If a button is pressed on the datasette, must switch motor on.
                     * $01-$FF: Motor is on.

$00C1-$00C2  STAL    Start address during SAVE to serial bus, LOAD and VERIFY from datasette and SAVE to datasette.
                     Pointer to current byte during memory test.

$00C3-$00C4  MEMUSS  Start address for a secondary address of 0 for LOAD and VERIFY from serial bus or datasette.
                     Pointer to ROM table of default vectors during initialization of I/O vectors.

$00C5        LSTX    Matrix code of key previously pressed

                     Values:

                     * $00-$3F: Keyboard matrix code.
                     * $40: No key was pressed at the time of previous check.

$00C6        NDX     Length of keyboard buffer

                     Values:

                     * $00, 0: Buffer is empty.
                     * $01-$0A, 1-10: Buffer length.

$00C7        RVS     Reverse mode switch

                     Values:

                     * $00: Normal mode.
                     * $12: Reverse mode.

$00C8        INDX    Length of line minus 1 during screen input. Values: $27, 39; $4F, 79.

$00C9        LSXP    Cursor row during screen input. Values: $00-$18, 0-24.

$00CA                Cursor column during screen input. Values: $00-$27, 0-39.


$00CB        SFDX    Matrix code of key currently being pressed

                     Values:

                     * $00-$3F: Keyboard matrix code.
                     * $40: No key is currently pressed.

$00CC        BLNSW   Cursor visibility switch

                     Values:

                     * $00: Cursor is on.
                     * $01-$FF: Cursor is off.

$00CD        BLNCT   Delay counter for changing cursor phase

                     Values:

                     * $00, 0: Must change cursor phase.
                     * $01-$14, 1-20: Delay.

$00CE        GDBLN   Screen code of character under cursor.

$00CF        BLNON   Cursor phase switch

                     Values:

                     * $00: Cursor off phase, original character visible.
                     * $01: Cursor on phase, reverse character visible.

$00D0        CRSW    End of line switch during screen input

                     Values:

                     * $00: Return character reached, end of line.
                     * $01-$FF: Still reading characters from line.

$00D1-$00D2  PNT     Pointer to current line in screen memory.

$00D3        PNTR    Current cursor column. Values: $00-$27, 0-39.

$00D4        QTSW    Quotation mode switch

                     Values:

                     * $00: Normal mode.
                     * $01: Quotation mode.

$00D5        LNMX    Length of current screen line minus 1. Values: $27, 39; $4F, 79.

$00D6        TBLX    Current cursor row. Values: $00-$18, 0-24.

$00D7        DATA    PETSCII code of character during screen input/output.
                     Bit buffer during datasette input.
                     Block checksum during datasette output.

$00D8        INSRT   Number of insertions

                     Values:

                     * $00: No insertions made, normal mode, control codes change screen layout or behavior.
                     * $01-$FF: Number of insertions, when inputting this many character next, those must be turned into control codes, similarly to quotation mode.

$00D9-$00F2  LDTB1   High byte of pointers to each line in screen memory (25 bytes)

                     Values:

                     * $00-$7F: Pointer high byte.
                     * $80-$FF: No pointer, line is an extension of previous line on screen.

$00F3-$00F4  USER    Pointer to current line in Color RAM.

$00F5-$00F6  KEYTAB  Pointer to current conversion table during conversion from keyboard matrix codes to PETSCII codes.

$00F7-$00F8  RIBUF   Pointer to RS232 input buffer

                     Values:

                     * $0000-$00FF: No buffer defined, a new buffer must be allocated upon RS232 input.
                     * $0100-$FFFF: Buffer pointer.

$00F9-$00FA  ROBUF   Pointer to RS232 output buffer

                     Values:

                     * $0000-$00FF: No buffer defined, a new buffer must be allocated upon RS232 output.
                     * $0100-$FFFF: Buffer pointer.

$00FB-$00FE  FREKZP  Unused (4 bytes).

$00FF-$010A  BASZPT  Buffer for conversion from floating point to string (12 bytes.)

$0100-$01FF          Processor stack. Also used for storing data related to FOR and GOSUB.

$0100-$013D  BAD     Pointers to bytes read with error during datasette input (62 bytes, 31 entries).

$0200-$0258  BUF     Input buffer, storage area for data read from screen (89 bytes).

$0259-$0262  LAT     Logical numbers assigned to files (10 bytes, 10 entries).

$0263-$026C  FAT     Device numbers assigned to files (10 bytes, 10 entries).

$026D-$0276  SAT     Secondary addresses assigned to files (10 bytes, 10 entries).

$0277-$0280  KEYD    Keyboard buffer (10 bytes, 10 entries).

$0281-$0282  MEMSTR  Pointer to beginning of BASIC area after memory test.

                     Default: $0800, 2048.

$0283-$0284  MEMSIZ  Pointer to end of BASIC area after memory test.

                     Default: $A000, 40960.

$0285        TIMOUT  Unused. (Serial bus timeout.)

$0286        COLOR   Current color, cursor color

                     Values: $00-$0F, 0-15.

$0287        GDCOL   Color of character under cursor

                     Values: $00-$0F, 0-15.

$0288        HIBASE  High byte of pointer to screen memory for screen input/output.

                     Default: $04, $0400, 1024.

$0289        XMAX    Maximum length of keyboard buffer

                     Values:

                     * $00, 0: No buffer.
                     * $01-$0F, 1-15: Buffer size.

$028A        RPTFLG  Keyboard repeat switch

                     Bits:

                     * Bits #6-#7:
                         * %00 = Only cursor up/down, cursor left/right, Insert/Delete and Space repeat
                         * %01 = No key repeats
                         * %1x = All keys repeat.

$028B        KOUNT   Delay counter during repeat sequence, for delaying between successive repeats

                     Values:

                     * $00, 0: Must repeat key.
                     * $01-$04, 1-4: Delay repetition.

$028C        DELAY   Repeat sequence delay counter, for delaying before first repetition

                     Values:

                     * $00, 0: Must start repeat sequence.
                     * $01-$10, 1-16: Delay repeat sequence.

$028D        SHFLAG  Shift key indicator

                     Bits:

                     * Bit #0: 1 = One or more of left Shift, right Shift or Shift Lock is currently being pressed or locked.
                     * Bit #1: 1 = Commodore is currently being pressed.
                     * Bit #2: 1 = Control is currently being pressed.

$028E        LSTSHF  Previous value of shift key indicator

                     Bits:

                     * Bit #0: 1 = One or more of left Shift, right Shift or Shift Lock was pressed or locked at the time of previous check.
                     * Bit #1: 1 = Commodore was pressed at the time of previous check.
                     * Bit #2: 1 = Control was pressed at the time of previous check.

$028F-$0290  KEYLOG  Execution address of routine that, based on the status of shift keys, sets the pointer at memory address $00F5-$00F6 to the appropriate conversion table for converting keyboard matrix codes to PETSCII codes.

                     Default: $EB48.

$0291        MODE    Commodore-Shift switch

                     Bits:

                     * Bit #7: 0 = Commodore-Shift is disabled; 1 = Commodore-Shift is enabled, the key combination will toggle between the uppercase/graphics and lowercase/uppercase character set.

$0292        AUTODN  Scroll direction switch during scrolling the screen

                     Values:

                     * $00: Insertion of line before current line, current line and all lines below it must be scrolled 1 line downwards.
                     * $01-$FF: Bottom of screen reached, complete screen must be scrolled 1 line upwards.

$0293        M51CTR  RS232 control register

                     Bits:

                     * Bits #0-#3: Baud rate, transfer speed. Values:
                         * %0000: User specified.
                         * %0001: 50 bit/s.
                         * %0010: 75 bit/s.
                         * %0011: 110 bit/s.
                         * %0100: 150 bit/s.
                         * %0101: 300 bit/s.
                         * %0110: 600 bit/s.
                         * %0111: 1200 bit/s.
                         * %1000: 2400 bit/s.
                         * %1001: 1800 bit/s.
                         * %1010: 2400 bit/s.
                         * %1011: 3600 bit/s.
                         * %1100: 4800 bit/s.
                         * %1101: 7200 bit/s.
                         * %1110: 9600 bit/s.
                         * %1111: 19200 bit/s.
                     * Bits #5-#6: Byte size, number of data bits per byte; %00 = 8; %01 = 7, %10 = 6; %11 = 5.
                     * Bit #7: Number of stop bits; 0 = 1 stop bit; 1 = 2 stop bits.

$0294        M51CDR  RS232 command register

                     Bits:

                     * Bit #0: Synchronization type; 0 = 3 lines; 1 = X lines.
                     * Bit #4: Transmission type; 0 = Duplex; 1 = Half duplex.
                     * Bits #5-#7: Parity mode. Values:
                         * %xx0: No parity check, bit #7 does not exist.
                         * %001: Odd parity.
                         * %011: Even parity.
                         * %101: No parity check, bit #7 is always 1.
                         * %111: No parity check, bit #7 is always 0.

$0295-$0296  M51AJB  Default value of RS232 output timer, based on baud rate

                     (Must be filled with actual value before RS232 input/output if baud rate is "user specified" in RS232 control register, memory address $0293.)


$0297        RSSTAT  Value of ST variable, device status for RS232 input/output

                     Bits:

                     * Bit #0: 1 = Parity error occurred.
                     * Bit #1: 1 = Frame error, a stop bit with the value of 0, occurred.
                     * Bit #2: 1 = Input buffer underflow occurred, too much data has arrived but it has not been read from the buffer in time.
                     * Bit #3: 1 = Input buffer is empty, nothing to read.
                     * Bit #4: 0 = Sender is Clear To Send; 1 = Sender is not ready to send data to receiver.
                     * Bit #6: 0 = Receiver reports Data Set Ready; 1 = Receiver is not ready to receive data.
                     * Bit #7: 1 = Carrier loss, a stop bit and a data byte both with the value of 0, detected.

$0298        BITNUM  RS232 byte size, number of data bits per data byte, default value for bit counters.

$0299-$029A  BAUDOF  Default value of RS232 input timer, based on baud rate

                     (Calculated automatically from default value of RS232 output timer, at memory address $0295-$0296.)

$029B        RIDBE   Offset of byte received in RS232 input buffer.

$029C        RIDBS   Offset of current byte in RS232 input buffer.

$029D        RODBS   Offset of byte to send in RS232 output buffer.

$029E        RODBE   Offset of current byte in RS232 output buffer.

$029F-$02A0  IRQTMP  Temporary area for saving pointer to original interrupt service routine during datasette input output

                     Values:

                     * $0000-$00FF: No datasette input/output took place yet or original pointer has been already restored.
                     * $0100-$FFFF: Original pointer, datasette input/output currently in progress.

$02A1        ENABL   Temporary area for saving original value of CIA#2 interrupt control register, at memory address $DD0D, during RS232 input/output.

$02A2        CASTON  Temporary area for saving original value of CIA#1 timer #1 control register, at memory address $DC0E, during datasette input/output.

$02A3-$02A4          Unknown.

$02A5        LINTMP  Number of line currently being scrolled during scrolling the screen.

$02A6        PALNTS  PAL/NTSC switch, for selecting RS232 baud rate from the proper table

                     Values:

                     * $00: NTSC.
                     * $01: PAL.

$02A7-$02FF          Unused (89 bytes).

$0300-$0301  IERROR  Execution address of warm reset, displaying optional BASIC error message and entering BASIC idle loop.

                     Default: $E38B.

$0302-$0303  IMAIN   Execution address of BASIC idle loop.

                     Default: $A483.

$0304-$0305  ICRNCH  Execution address of BASIC line tokenizater routine.

                     Default: $A57C.

$0306-$0307  IQPLOP  Execution address of BASIC token decoder routine.

                     Default: $A71A.

$0308-$0309  IGONE   Execution address of BASIC instruction executor routine.

                     Default: $A7E4.

$030A-$030B  IEVAL   Execution address of routine reading next item of BASIC expression.

                     Default: $AE86.

$030C        SAREG   Default value of register A for SYS.
                     Value of register A after SYS.

$030D        SXREG   Default value of register X for SYS.
                     Value of register X after SYS.

$030E        SYREG   Default value of register Y for SYS.
                     Value of register Y after SYS.

$030F        SPREG   Default value of status register for SYS.
                     Value of status register after SYS.

$0310-$0312  USRPOK  JMP ABS machine instruction, jump to USR() function.

$0311-$0312  USRADD  Execution address of USR() function.

$0313                Unused.

$0314-$0315  CINV    Execution address of interrupt service routine.

                     Default: $EA31.

$0316-$0317  CBINV   Execution address of BRK service routine.

                     Default: $FE66.

$0318-$0319  NMINV   Execution address of non-maskable interrupt service routine.

                     Default: $FE47.

$031A-$031B  IOPEN   Execution address of OPEN, routine opening files.

                     Default: $F34A.

$031C-$031D  ICLOSE  Execution address of CLOSE, routine closing files.

                     Default: $F291.

$031E-$031F  ICHKIN  Execution address of CHKIN, routine defining file as default input.

                     Default: $F20E.

$0320-$0321  ICKOUT  Execution address of CHKOUT, routine defining file as default output.

                     Default: $F250.

$0322-$0323  ICLRCH  Execution address of CLRCHN, routine initializating input/output.

                     Default: $F333.

$0324-$0325  IBASIN  Execution address of CHRIN, data input routine, except for keyboard and RS232 input.

                     Default: $F157.

$0326-$0327  IBSOUT  Execution address of CHROUT, general purpose data output routine.

                     Default: $F1CA.

$0328-$0329  ISTOP   Execution address of STOP, routine checking the status of Stop key indicator, at memory address $0091.

                     Default: $F6ED.

$032A-$032B  IGETIN  Execution address of GETIN, general purpose data input routine.

                     Default: $F13E.

$032C-$032D  ICLALL  Execution address of CLALL, routine initializing input/output and clearing all file assignment tables.

                     Default: $F32F.

$032E-$032F  USRCMD  Unused.

                     Default: $FE66.

$0330-$0331  ILOAD   Execution address of LOAD, routine loading files.

                     Default: $F4A5.

$0332-$0333  ISAVE   Execution address of SAVE, routine saving files.

                     Default: $F5ED.

$0334-$033B          Unused (8 bytes).

$033C-$03FB  TBUFFR  Datasette buffer (192 bytes).

$03FC-$03FF          Unused (4 bytes).