Zilog Z80 playground

This is a scratchpad repository containing my Z80 sandbox.

Assembler

The most interesting for other people is most probably an assembler written in Python.

The assembler is more-than-two-pass assembler to make code more readable than optimized.

I've also written a 2-pass Z80 assember in C which is much faster. Check it out here.

Z80 Minicomputer

For now the other part of the project consists of:

• a main board with 10 MHz Zilog Z80 CPU and some LEDs,
• a RAM board with two 62256 SRAM chips, 32 kiB of memory each and 7-segment displays showing data and address bus state,
• a CLKMOD board acting as a clock and interrupt controller.

Implying the following specs:

- Up to 1 MHZ Z80 CPU (because of bottleneck that is CLKMOD which will
                       be replaced with a crystal oscillator)
- 64 kiB SRAM
- No external non-volatile memory
- No IO at the moment

At the moment I'm developing the new IO Controller and IO device modules:

• 128x160 TFT display module,
• PS/2 keyboard input module.

In the legacy/ directory there are some IO controller files which I used for communicating with the CPU via serial port and low-resolution VGA output.

Files

• z80asm – Python dual-syntax (i8080, Z80) assembler/disassembler module

• busctl/ – Bus controller (and RAM Uploader)

• clkmod/ – Clock emulator

• fontmaker/ – Little HTML/JS utility for creating fonts

• legacy/ – Old unused controllers

• lib/ – ASM libraries

• schematics/ – KiCAD schematics

• static/ and templates/ – Flask assets

• tft – TFT Display Controller

• ctl.py – Flask GUI for the clock emulator

• prog.py – Bus controller RAM programming interface

• serialprompt.py – Utility for fast testing of serial communication

Resources

• https://maker.pro/pic/projects/z80-computer-project-part-1-the-cpu
• https://istvannovak.net/2018/01/25/zx-spectrum-ide-part-3-a-brief-overview-of-the-z80a-cpu/