arduino-6502

6502 emulator/simulator for Arduino

THIS PROJECT IS STILL IN DEVELOPMENT, MANY FEATURES ARE NOT YET IMPLEMENTED.

List of contents

1. Features
2. Info
3. Get Started
4. License

Features

• 6502 CPU Simulator with all registers, pins (appart from VDD, VSS and NC), instructions and processor status flags from the last version of the processor, the W65C02S (for Arduino Mega)
  • (Optional) RAM/ROM Simulator (for Arduino Uno), with only 11 address bus pins.
• 6502 CPU Emulator in C++ (without Arduino)

Info

6502 CPU Simulator

• Arduino/6502 PIN table:

Arduino PIN(s)	6502 Function
23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49, 51, 53	ADDRESS BUS (A0-A15)
8	BUS ENABLE (BE)
22, 24, 26, 28, 30, 32, 34, 36	DATA BUS (D0-D7)
3	INTERRUPT REQUEST (IRQB)
4	MEMORY LOCK (MLB)
5	NON-MASKABLE INTERRUPT (NMIB)
-	NO CONNECT (NC)
9	PHASE 2 IN (PHI2)
11	PHASE 2 OUT (PHI2O)
2	PHASE 1 OUT (PHI1O)
7	READ/WRITE (RWB)
A1	READY (RDY)
12	RESET (RESB)
10	SET OVERFLOW (SOB)
6	SYNCHRONIZE WITH OPCODE FETCH (SYNC)
-	POWER (VDD) AND GROUND (VSS)
A0	VECTOR PULL (VPB)

RAM/ROM Simulator (optional)

• Arduino PIN table:

Arduino PIN(s)	Function
13, 12, 11, 10, 9, 8, A0, A1, A2, A3, A4	ADDRESS BUS (A0-A10)
0, 1, 2, 3, 4, 5, 6, 7	DATA BUS (D0-D7)
A5	READ/WRITE (RWB)

• Memory map:

Memory Address(es)	Function
0x0000-0x00FF	Zero Page (RAM)
0x0100-0x01FF	Stack (RAM)
0x0200-0x03FF	RAM
0x0400-0x06F9	ROM
0x06FA/0x06FB	Addresses of the non-maskable interrupt handler (ROM)
0x06FC/0x06FD	Power/reset location (ROM)
0x06FE/0x06FF	BRK/Interrupt request handler (ROM)

Note: You don't have to worry about the last addresses being mapped to 0x06FA... (instead of 0xFFFA...) because the memory simulator will do the translation. The processor still fetches from 0xFFFa... If you have your own RAM/ROM/IO chip everything should work as expected and you can map them as you wish.

Get Started

• For the CPU/Memory Simulator (Arduino):

  1. Clone the repo
  2. Go into the directory simulator (romram-sim for memory)
  3. arduino-cli board list to get the port Arduino Mega (Uno for memory) is connected to
  4. arduino-cli board attach [port]
  5. sudo make to compile and upload the code to the Arduino.

• For CPU Emulator (Without Arduino):

  1. Clone the repo
  2. Go into the directory emulator
  3. Compile with g++ cpu.cpp

License

The source code is licensed under the open source GPL v3.0. License is available here.