Assemulator

Assemulator gives you an assembler and emulator for custom CPUs by implementing some simple functions.

I have designed a few toy CPUs, and it is tedious to write an assembler and emulator each time.

Assembler features

• Global and local labels
• Macros
• Expression evaluation: (1 + label) * 4, symbol >> 0xff, etc.
• Namespaced file inclusion e.g. string: .include "string.asm"
• Assembler directives
• Conditional assembly
• Helpful error messages

Emulator features

• Real-time user input for games via 6 buttons (arrow keys and ZX)
• Prompt user input from stdin
• Print characters and integers to stdout
• Generate random numbers
• Bitmap screen

Example

examples/risc16/main.rs shows an example implementation for a simple 8 instruction, 16-bit, load-store CPU. It implements the following Processor trait:

fn new(program_counter: u64, program: Vec<u8>, data: Vec<u8>) -> Self;
fn parse(address: u64, opcode: Opcode, arguments: &[Argument]) -> Result<Vec<u8>, String>;
fn step(&mut self) -> usize;

...allowing us to write programs such as:

; 8x8=8 bit shifting multiplication
; r1: product
; r2: multiplicand
; r3: multiplier
; r4: mask
; r5: mask & multiplier

.doadd: add r1, r2              ; product += multiplicand
.loop:  add r2, r2              ; multiplicand <<= 1
        add r4, r4              ; mask <<= 1
        beq r4, r0, .end        ; if mask == 0, end
multiply:
        and r5, r3, r4          ; r5 = mask & multiplier
        beq r5, r4, .doadd
        beq r0, r0, .loop       ; .loop is a local label
        
.end:   st r1, r0, ticker       ; print the value

Features planned / in progress

• Fixed-point constants (i0.8, i5.3, i8.16, i32.32, etc.)
• Step debugging
• Directives
  • org: start code at specific address
  • align: round symbol address up to multiple of align
  • zero: fill with n bytes of zeros
• Prettier emulator interface
• Graphics for the emulator