A simple 8bit breadboard computer emulator

Emulating Ben Eater's 8 bit breadboard computer.
Build the project by running ./build.sh, this will create a ./main binary using g++.

The main program is capable to load .bin and .out binary files as well as assembly language source files, either from command line arguments or from user input.

Run the program using ./main <file path> <clock speed in hertz>

The CPU

These are the eleven opcodes Ben Eater built into his instruction set:

Opcode	Mnemonic	Description	Affect Flags	Affect Registers
0	NOP	Do nothing for one instruction cycle	none	none
1	LDA	Loads contents of a memory address to the A register	none	A
2	ADD	Adds the A register with the contents of a memory address	C Z	B A
3	SUB	Substracts the A register with the contents of a memory address	C Z	B A
4	STA	Stores the A register at a memory address	none	none
5	LDI	Loads a 4 bit immediate value to the A register	none	A
6	JMP	Unconditionnal jump to a memory address	none	PC
7	JC	Jumps to a memory address if Carry flag is set	none	PC *
8	JZ	Jumps to a memory address if Zero flag is set	none	PC *
E	OUT	Loads the A register onto the OUT register and sets the OE flag	OE	OUT
F	HLT	Sets the HALT flag, used to halt program execution	HALT	none

* only if jumping

Flag	Description	Behavior
Z	Zero	Set when an operation returns a zero
C	Carry	Set when an operation's result was larger than 255
HALT	Halt	Set by a HLT instruction, only cleared on reset
OE	Output Enabled	Set by an OUT instruction and cleared by the next instruction
IIE	Invalid Instruction Exception	Indicates the byte read by the cpu was not a valid instruction

Memory can easily be expanded and more opcodes can be added by modifying cpu.h and cpu.cpp.

Assembler Syntax

The assembler is based off a simplified version of Volker Barthelmann's vasm oldstyle syntax module - used a lot in Eater's 6502 videos.
As of now it implements labels as well as the .org and .byte directives.
Anything following ; is ignored and considered a comment.

Number format

Numbers preceded by $ are hexadecimal, while a preceding % designate a binary number.
The assembler also accepts octal values preceded by @, and a digit followed by a # can be used to define an arbitrary base between 2 and 9.
Bare numbers default to decimal.

Labels

Labels are symbols that refer to a memory address using a user-defined mnemonic. They must be defined on a new line and terminated by :
Refer to a label by writing its name in lieu of a memory address.

The assembler is case insensitive, meaning a lower case symbol is identical to upper case.

Directives

The .org and .byte directives are available to use:

Usage	Description
.org [#]adr	Sets the base address for the following code block. Accepts an optional #
.byte int1[ int2...]	Writes the following numbers, separated by a blank space, into successive bytes of memory

An alternative to the .byte directive is writing decimal integers with no symbol/mnemonic preceding them:

.byte 8   ; Writes an 8 at the current memory location
8         ; Also writes an 8

$F        ; Will not work
.byte $F  ; But this will

Example program: adding 28 and 14

A simple program adding two numbers that are located at the end of memory would look something like this:

  lda $e
  add $f
  out
  hlt
.org $e
  .byte 28 14