My Z280 Board

I lived close to and worked in Silicon Valley, California for three years in the heady days of the early 1990's.  It was an exciting place to work in and explore.  My work allowed me time to visit various different companies and places.  One that I managed to visit was Zilog - the maker of the Z80 CPU chip.  My first computer - the Tandy TRS-80 Model 1 (it was the first computer one could purchase in Western Australia back in 1978 or '79).  I fell in love with the assembly code, writing my own and extending other peoples code. Yes, thousands of hours where sent in front of the computer.  Apart from typing in BASIC games from Byte and Micro-80 magazines, I managed to complete ZORK-I.

My next computer was an Epson QX-10.  This beauty could bank select 64KB from a total of 256KB!  What power!  It was way ahead of it's time, as it came with integrated WSIWIG word processor, graphics program and a spreadsheet program.

With a few phone calls to Zilog, pleading for a tour form an Australian visitor, they eventually relented.  I spent a delightful hour touring the facility and came away with a Z280 chip, a plotter drawing of a chip and a 4" partially etched wafer that I still have to this day.

Since there was no web based Internet back in those days, so information was hard to come by on how to use the chip.  I Eventually managed to purchase a second hand Z280 manual from one of the wonderful monthly Bay Area electronic/computer flea markets.  I would also visit computer/electronic resellers that would buy entire assembly lines from companies that had gone under.  The resellers would then sell off the gear at tagged prices, that over time if they didn't sell quick enough, would then be sold off by the pound (weight) and eventually end up at 25 cents per pound.  I would keep an eye on items and swoop in when it got down to 50 cents or so per pound.   I ended up with some interesting prototypes and thousands of TTL-LS based chips.

I modded some ones breadboard to allow me to extend the QX-10 ISA like bus out onto the bread board.  I designed and built bus buffering circuitry, that cleaned up the bus signals after their 20cm journey.  In those days I used the breadboard for a few projects, such as a heart rate monitor, voice recorder that allowed me to reverse the audio, or speed it up or down, the Z280 board, audio Fast Fourier Transformations (FFT).  I will have dig around to see what documentation I might have still filed away on these projects.  Unfortunately, I didn't take enough photographs of them.

Wanting to do something with the Z280 chip, I built the build pictured below. It was designed as a proof of concept, it allowed me to boot it via a program that was downloaded via the Epson QX10 serial port and report back to the computer that it had booted up correctly.

The board below is missing the MAX-232 serial buffer chip.  There is an empty socket next to where it should go.  I don't remember what it was meant to be for.  The large male DIL sockets where for a proposed daughter card that I never got around to designing or building.

and the hand soldered bottom:

and the all important Z280 Technical Manual:

Someone contacted me with a website of the Z280 manual, but it turned out that it was missing pages 6.4 and 6.5, so I have photographed them and attached them below.

All the best with your Z280 project (your only here because your working on one right?  ;-)   Love to hear what you doing with yours.