Simple board based on Z80 CPU and 'modern' Arduino board

Click here to have a look at the videos about variants

This project has a few purpouses:

• learn old assembly language for Intel 8080
• learn the features for z80
• replace ROM with bootloader based on Arduino
• use Arduino as app loader for RAM area
• use Arduino as simple serial IO for CPU

Project is making step by step from simplest minimal to more complicated.

All files for each variant you can find in directory variants

Variant difference

Each variant has own directories:

• arduino - for arduino scketches (with preloaded Z80 binary)
• Assm - assembly files and binares
• doc - some useful instructions

Also each project has Kicad schematics and Readme with requirements for that variant.

Clone this repository

git clone https://github.com/maks-ushakov/z80-simple-board.git

Choose variant you want to use.

Load Arduino sketch

Use Variant readme to change preloaded memory. Change Memory array with z80 C-style-array code you want to be loaded to z80 memory

Load sketch to arduino

You can use any file extensions for sourse and binary files. Common extensions for sourses are .s, '.asm', 'z80', for binary are .bin or none, lst for listing files. I use .z80 for assembly source and bin for binary.

If you have z80asm

z80asm --output=<file_name>.bin <file_name>.z80

If you use VASM

vasmz80_oldstyle -Fbin -o <file_name>.bin -Lall -L <file_name>.lst <file_name>.z80

vasmz80_std -Fbin -o <file_name>.bin -Lall -L <file_name>.lst <file_name>.z80

Online

By asm80 or ORG IDE

xxd -g 1 <file_name>.bin

xxd -i <file_name>.bin

Minicom

minicom -b 9600 -D /dev/ttyUSB0

Screen

screen /dev/ttyUSB0 9600

If you do not have access to ttyUSB0 (Arduino or terminal app still connect to /dev/ttyUSB0)

fuser -k /dev/ttyUSB0

use command P or M to load values started by address

> P <addr> <data> <data> <data> ...

> m <addr> <data> <data> <data> ...

to check memory use command D

> D <start_addr> <end_addr>

// TODO

Test. First run.

Arduino Nano as Clock generator and Buffer.

Resources: variants/test

Arduino as Memory and IO port. Minimal System. 16B memory. Any IO port is Arduino Arduino as universal chipset.

Resources:variants/minimal_16B

Arduino as Memory loader and simple OS Minimal System, 32B memory. Arduino has command line interface to load code

Resources: `variants/minimal_32_64B`

• More memory 32B or 64B. Arduino Console

• LCD as IO port. Bus Buffering (in progress)

• Mocked memory with multiplexer/commutator (in progress)

• 32k RAM chip. DMA. CPU give acces to bus (featured)

• Block load XMODEM (featured)

• Monitor (BIOS) via Arduino Serial (featured)

• PPA 8255. Address detector. (featured)

-Timer 8253 and Interrupt controller (featured)

Links:

z80 User Manual

Arduino Language References

Arduino Pinout

z80 info - a lot of information about z80, his perioferial chips instruction sets and tutorials

VASM - portable assembler for different CPUs

ORG IDE - online z80 IDE

asm80 - online IDE and emulator

Other z80 projects when I get some ideas, shematic principles and code examples:

Grant Searl z80 system some boards has CP/M and BASIC, they used serial terminal

Wichit Sirichote z80 kit has z80 binary for Monitor(BIOS)

Wichit Sirichote i8085 kit has Assembly source code for Monitor(BIOS)

CPU ville

Books (some books you can find on z80 info Books):

Build your own Z80 computer. Design guidelines and application notes. Ciarcia, S. 1981

Programming the Z80. Zaks Rodnay, 1981

From homemade devices on logic elements to microcomputers. USSR. Bartenev V., Alginin B. 1993 (About i8080)

Simplest micro-ECM. USSR. Bureev L.N. 1989 (About i8080 with simplest BIOS)