This project allows you to test a Z80 CPU. Two models are currently available. Both function essentially the same and use the same code except for one line. "Model 1" uses a less common 74ALS990, which, while not easy to obtain, is quite practical to use. "Model 2" replaces this IC with two more common ones and adds some pin headers for your own experiments.
It tries
- to identify the CPU technology (NMOS/CMOS),
- to identify the CPU manufacturer,
- to test whether the CPU is still functional,
and helps
- to find out the max. supported clock rate.
The above results will help to identify fake CPUs.
It does not test
- Interrupts
- WAIT and HALT signals
- M1 and RFSH signals
- BUSRQ and BUSACK signals
The hardware has following features:
- 32kb EPROM (27C256), alternatively AT29C256 Flash Memory can be used (an AT28C256 is not pin compatible)
- 32kb SRAM
- 2 output ports (1x unidirectional, 1x read-back) with 16 LEDs
- RESET and NMI button
- 16 MHz / 20 MHz switchable
- 1, 1/2, 1/4, 1/8, 1/16 multiplicator (1-16 MHz / 1.25-20 MHz)
- Connectors for measuring CPU power consumption
- USB powered
- THT for easy soldering
This project is based on an idea of
- https://oshwlab.com/vitalian1980/z80-tester (Hardware, Public Domain)
and additionally based on ideas of
- https://bitbucket.org/rudolff/z80-tester (Software, no license)
- https://github.com/djtersteegc/z80-cmos-nmos-tester (MIT license)
- https://github.com/skiselev/z80-tests (Software, GPL-3.0 license)
- https://github.com/EtchedPixels/FUZIX/blob/master/Applications/util/cpuinfo-z80.S (Software, GPL-2.0 license)
- https://groups.google.com/g/retro-comp/c/rhKeKpXmAXM (Software, no license)
- https://www.malinov.com/sergeys-blog/z80-type-detection.html (Software, no license)
and finally Frank Cringle's Z80 instruction set exerciser
- https://github.com/begoon/z80exer (Software, GPL-2.0 license)
[Please check the licence files in the relevant directories. When you are interested in a PCB, please contact me.]
The project uses KiCAD and zmac.
Zilog Z84C0020PEC from a Chinese marketplace. It is a U880 (running with 10 MHz):
