iz6502 - 6502 and 65c02 and 65c24T8 emulator in Go

6502 and 65c02 emulator library for Go, extended to support the mythical 65c24T8

It is being used in:

• Apple II emulator izapple2

See the library documentation in pkg.go.dev

Example

package main

import (
	"github.com/lunarmobiscuit/iz6502"
)

func main() {
	// Prepare cpu and memory
	memory := new(iz6502.FlatMemory)
	cpu := iz6502.NewNMOS6502(memory)

	// Load program the memory
	memory.Poke(0x0000, 0xe8) // INX
	memory.Poke(0x0001, 0x4c) // JMP $0000
	memory.Poke(0x0002, 0x00)
	memory.Poke(0x0003, 0x00)

	// Set inital state
	cpu.SetTrace(true)
	cpu.SetAXYP(0, 0, 0, 0)
	cpu.SetPC(0x0000)

	// Run the emulation
	for {
		cpu.ExecuteInstruction()

		_, x, _, _ := cpu.GetAXYP()
		if x == 0x10 {
			// Let's stop
			break
		}
	}
}

Test suites

The emulation is instruction based and has been tested with:

• Klaus Dormann functional tests
• Tom Harte ProcessorTests for 6502 and 65c02. Some flag N errors remain for ADC using binary coded decimal mode.

24T8 Funcationality

See https://github.com/lunarmobiscuit/verilog-65C2424-fsm and https://github.com/lunarmobiscuit/verilog-65C24T8-fsm for descriptions of the changes from the WDC65C02

In short, this mythical variation of the 65xx CPU extends the address space to 24 bits, extends the registers to 8, 16, or 24 bits, and adds 8 copies of the registers to implement 8 threads with two-cycle context switches