This is a rudimentary 8-bit micro-computer, based on the Zilog Z80 processor. It has a single 2kb EEPROM chip, and an extremely simple output device which latches and shows the contents of the data bus, when the CPU executes an OUT instruction to any I/O address.
The nice thing about such a simple computer, is that it can demonstrate the way a computer operates very clearly. You can step the clock manually with the big button, to watch step-by-step as each instruction is fetched and executed.
In fact you can watch a
video where I'm manually stepping the clock, while explaining
step-by-step the execution of this very simple program:
org $0
ld a, 1
loop: out (255), a
rlca
jr loop
There's also a
followup video, where I added a proper running clock,
and a slightly more interesting program:
org $0
ld a, 1
left: out (255), a
rlca
cp 128
jr z, right
jr left
right: out (255), a
rrca
cp 1
jr z, left
jr right
More photographs of the PCB construction process. This was the first time I used the UV-sensitive board method, and also the first time I tried applying solder-mask (also UV-curable). The result is not perfect, but I think it looks cool.
Copyright (C) 2016 John Tsiombikas.
Feel free to use anything from this project, under the terms of the
Creative Commons Attribution-ShareAlike license.
