munch

A 6502 emulator.

Usage

package main

import (
	"github.com/noddy76/munch"
)

var rom = []uint8{
	0xa9, 0x01, //       LDA #$01
	0x8d, 0x00, 0x02, // STA $0200
	0xa9, 0x05, //       LDA #$05
	0x8d, 0x01, 0x02, // STA $0201
	0xa9, 0x08, //       LDA #$08
	0x8d, 0x02, 0x02, // STA $0202
}

func main() {
	bus := munch.NewBus()
	bus.Addressable(0x0000, 0x3fff, munch.NewRam(0x40000))
	bus.Addressable(0x8000, 0x8fff, munch.NewRom(rom))
	bus.Addressable(0xfffa, 0xffff, munch.NewRom([]uint8{0x00, 0x00, 0x00, 0x80, 0x00, 0x00}))

	cpu := munch.NewCpu6502(bus)

	cpu.Debug = true

	for cpu.PC != uint16(0x8000+len(rom)) {
		bus.Tick()
	}
}

When run (because debug output from the CPU was turned on) you should see.

8000    LDA #$01                  PC:8002 A:01 X:00 Y:00 SP:fd nv‑BdIzc
8002    STA $0200                 PC:8005 A:01 X:00 Y:00 SP:fd nv‑BdIzc
8005    LDA #$05                  PC:8007 A:05 X:00 Y:00 SP:fd nv‑BdIzc
8007    STA $0201                 PC:800a A:05 X:00 Y:00 SP:fd nv‑BdIzc
800a    LDA #$08                  PC:800c A:08 X:00 Y:00 SP:fd nv‑BdIzc
800c    STA $0202                 PC:800f A:08 X:00 Y:00 SP:fd nv‑BdIzc

The central element is the bus. You can attach Addressables to the bus sunch as the Ram and Rom objects in this package. When the Cpu6502 is created registers itself as a Ticker with the bus. From then on every time Tick() is called on the Bus the call is propogated to every registered Ticker object.

References

• Fergulator A NES emulator written in Go
• redcode's 6502 A portable 6502 emulator written in C
• Nesdev Wiki