rust16vm

A 16bit virtual machine with 8 registers.

• Current instructions:
  • MOV
  • ADD/SUB/MUL/DIV
  • STR
  • LDR
  • JMP
  • EQ/NEQ/LT(E)/GT(E)

Specs

The VM uses 16bit wide instructions, loaded previusly at the memory, each instruction occupies 2 bytes in memory. It executes a naive fetch/decode/executes loop.

Register A, B and C are General Purpose registers. Register M, SP, BP, PC, FLAGS are reserved.

A simple for loop

Here is a small example on how the virtual machine can run an arbitrary set of instructions:

1. You can use the macro rv16asm! under the src/asm module to parse the instructions to binary that the VM can understand and execute

let program = rv16asm! {
  "MOV A, #0",

  "EQ A, #10",   // loop
  "CJP #10",
  "ADD A, #1",
  "JMP #2",      // jmp to instruction at addr 2

  "ADD FLAGS, #1" // halts machine
};

let mut mem = LinearMemory::new(1024);

for (idx, inst) in program.iter().enumerate() {
  assert!(mem.write2((idx * 2) as u16, *inst));
}

let mut machine = Machine::new(mem);
while let Ok(_) = machine.step() {
  machine.print_regs();
}

assert_eq!(machine.registers[Register::A as usize], 10);