I’m excited to announce a very cool project for retromaniacs:

RetroShield is an 8-bit microprocessor daughtercard for Arduino Mega. A real 8-bit microprocessor executes programs, while Arduino Mega emulates RAM, ROM, and peripherals.

Hardware/Arduino Software for 6 microprocessors released (see below for hw/sw details): MOS: 6502 Motorola: 6809 Intel: 8031 - 8085 RCA: 1802 Zilog: Z80

Upcoming microprocessors (bold chips at hand):

Fairchild: F8 Intel: 4004 , 4040 , 8008 , 8080 , 8088 , MCS-48 (the whole line-up :)) Intersil: 6100 or 6120, Harris HD6120 (PDP-8) Motorola: 6800, 6801/ 6803 , 68008 National: SC/MP, SC/MP II Signetics: 2650 , 8X300 Texas Instruments TMS9900 Commodore SID Let me know if you want anything else to be added to the list. Donations are welcome.

Hardware Specs: Microprocessor runs at about 110~170kHz. RAM : ~6 KB (available in Arduino Mega, expandable to 128 KB via expansion ROM : >200 KB (available in Arduino Mega) Peripherals: UART, PIA, Timers, etc. (emulated by Arduino)

Project goal is to make a simple platform to keep microprocessors alive No need to build complex circuits, or burn EEPROMs :) If you have the chip, you can bread-board it in one night. Existing Arduino shields can be used to extend the capabilities, i.e. SDCard, LCD. You can learn how microprocessors interface w/ memory or peripherals. Run some of the great older software avaliable.

Open source hardware/software.

Status

Microprocessor Emulated Hardware Software 6502 / W65C02S Apple-1 (6502+6521)

KIM-1 (6502 + 6530) MON,BASIC,Cassette (Steve W)

KIM-1 (MOS Technology, Inc) 6809 6809E + FTDI Simon6809 (Lennart Benschop) Z80 Z80 + 8251 Microsoft Basic (MSFT, Grant Searle)

EFEX (Mustafa Peker) 8031 8031 + UART PAULMON2 (Paul Stoffregen) 8085 8085A + 8251 MON85 (David Dunfield) 1802 1802 + UART MCSMP (Charles J, Yakym)

Tiny BASIC (Tom Pittman)

RCA BASIC3 (Ron Cenker) Signetics 2650 next Intel 8080 next Motorola 6801 / 6803 next Motorola 68008 next

2019/08/12: Released updated PCB’s for 1802 and 8031.

For 1802, connected Q directly to Arduino to decode uart (rev A design required a jumper cable from Q to Arduino).

For 8031, 8031 couldn’t drive an LED directly, so I rerouted the LED to the available Arduino GPIO.

Bit the bullet and ordered PCB Assembly service to solder SMT parts on PCB’s to make it easier to build this thing.



Hardware Details

Schematics, PCB, gerber files are available at RetroShield-HW.

I use GEDA gschem & pcb.

My hope is people will be able to contribute hw/sw so we have many flavors to experience.

Arduino Code

Links to Arduino Code for each microprocessor:

Software Details:

RetroShield 6502 Theory of Operation

RetroShield 6809 Theory of Operation

Theory of Operation for Z80, 1802, 8031, 8085 will be completed as needed (frankly same concept as 6502 and 6809).

Kit/PCB’s

PCB/Kits are available for sale at my store

your purchase helps support more microprocessors

License Information

Copyright 2019 Erturk Kocalar, 8Bitforce.com

Hardware is released under Creative Commons ShareAlike 4.0 International.

Software is released under the MIT License.

Distributed as-is; no warranty is given.



The Force

6502 6809E Z80