CPU Emulator

Simple CPU emulator written in Rust

The instruction set implemented in this program is from this page (only difference is that STO is STA).

Instruction list

Name	Code	Opcode	Definition
Load	LDA XY	1XY	Load the memory address of XY into the accumulator
Store	STA XY	2XY	Store accumulator value in memory address XY
Add	ADD XY	3XY	Add value of memory address XY to accumulator
Subtract	SUB XY	4XY	Subtract the value of memory address XY from accumulator
Input	IN	500	Take user input and store in accumulator
Output	OUT	600	Write value of accumulator to shell
Halt	HLT	700	Halt execution of the program
Set	SET XY	8XY	Set the loaded memory address (loaded via LDA) to the memory address of XY
Jump	JMP XY	9XY	Change the program counter to memory address XY
Call	CALL LABEL	N/A	This instruction internally changes into a JMP XY call to jump to a label.

Example programs

Add two numbers

MAIN:
	CALL GETINPUTS
    CALL ADDNUMS
    CALL PRINTOUT

GETINPUTS:
	IN
	STA 50
	IN
	STA 51

ADDNUMS:
	LDA 50
	ADD 51
	STA 52

PRINTOUT:
	LDA 52
	OUT
	HLT

Subtract one number from another

MAIN:
	CALL GETINPUTS
    CALL SUBTRACT
    CALL PRINTOUT

GETINPUTS:
	IN
	STA 50
	IN
	STA 51

SUBTRACT:
	LDA 50
	SUB 51
	STA 52

PRINTOUT:
	LDA 52
	OUT
	HLT

Infinite get input & print loop

MAIN:
	CALL LOOP

LOOP:
	IN
	OUT
	CALL LOOP

Pre-defining data

MAIN:
	LDA 50
	ADD 51
	OUT
	HLT

50 DAT 10
51 DAT 11

The above code means that at address 50, the number 10 will be stored, and at address 51, the number 11 will be stored. Upon execution 50 will be loaded into the accumulator, 51 will then be added to the accumulator and the accumulator will be outputted. Followed by a halt instruction.

Execution

1. Build the binaries
2. ./path/to/binary --compile source.file target.file
3. ./path/to/binary --run target.file