In this DIY Hacking series, we will actually build a computer based around the Z80 CPU. In the process, we'll learn how it works and how to program it! The Z80 processor was designed by Zilog (led.
After making the mod to the video O/P of my ZX81, as described here, I discovered that my TV would not successfully display a picture. This seems to be a common problem with non-CRT TVs so a solution was needed.
- This way, I can prove out most of the computer without relying on the Z80. Once the wiring is working, I can get the Z80 itself going as a separate step. The Teensy also controls the clock and reset of the Z80, so can act as a debugger, and even temporarily pause Z80 execution so it can read/write RAM while the Z80 is running.
- Retro Computing – About small SBC systems.
- After successfully building a Harlequin 128K, and chatting online to @6502Nerd, who has built his own homebrew computer based upon the 6502, I decided to have a crack at it. The aim of this project is to build a fully functioning Z80 based computer.
Just as I was thinking about doing a more intrusive mod I discovered the Minstrel ZX80 Clone project from Tynemouth Software. I ordered the PCB and it arrived the next day.
The PCB came complete with a comprehensive list of components together with suggested sources for the rarer ones. Strangely it didn’t come with a circuit diagram, which it should have done considering Tynemouth have modified the circuit.
Z80 Computer Trainer Kit
I have been through my component boxes and have a number of the required components already.
Although the Minstrel ZX80 Clone project is based on the ZX80 it is designed to fit into a ZX81 case. Fortunately I have a ZX81 I can use; I also have a ZX80 with an original ZX81 upgrade ROM I can install into the Minstrel PCB.
Z80 Projects
Next task is to order the missing components. Once the machine is working I will use it to test the diode PROM and basic LED output circuit.