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Z-80 Homebrew Computer - Introduction
Topic:Z-80   Date: 2003-07-05
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There are 12 parts to this article:
1 < 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12

This is certainly not a technically modern project. It is, however, a project that can literally be hacked together from garbage. Most of the parts were standard components twenty years ago, so not only are they cheap and available now, but you can find most of them on the previous generation of utility microcontrollers. Weird protocol converters, automation controllers, epoxy flow rate computers, and the like often used the Z-80.

My Z-80 homebrew computer consists of (6) Z-80 pios, (1) Z-80 cpu, (6) 74ls244s for fully buffered data, control and address bus, (8) latched and buffered 7 segment leds, (3) 2816/2716 2K byte EPROM/EPROM memories, (1) 6116 2kbyte ram memory, (2) 74ls154s for memory and io decoding, (1) 74c923 for decoding a 20 key keypad, and (36) incandescent 330 type midget flanged aircraft bulbs are mounted on a front panel display.

It has the most glorious lights:

I used point-to-point soldering and plain perfboard for the construction, because wire wrap was too expensive. If I did it over again, I'd probably use printed circuit boards, even if I had to wait a few years. Certainly, I would have paid more attention to my solder joints. I spent 10 years fixing bad solder joints on the homebrew. One thing I learned with later projects is that if you must use point-to-point soldering, at the very least get yourself a board with a donuts so that the joints don't move around as much. In the end, though, I was able to do it with perf board, but it was insane.

One thing that is unique about this particular version of homebrew computer vs. many of the ones that I saw in the late seventies and early eighties (they don't even try any more!) is that the bus is buffered and there are lots of i/o lines and expansion possibilities. This makes the project perfect for controlling tons of devices like displays and other stuff for your lab. This also gives me lots and lots of lights. More on that later.

I made a video of the homebrew computer running. The video starts after the power goes on. I then toggle reset, which runs the dump routine, and then it goes into a lamp/port test cycle. The dump routine is clocked by the 4th lamp from the left on the 3rd row down. The data going out to the PC is on the 4 lamps to the right on the 3rd row down. You can view the vid here.


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