A Little Bit of History and Background

March of 1982 the Space-Time Productions Single Board Computer design was copyrighted by Mr. Michael Lee Simon of Rockford, Illinois. [ Mr. Simon continues to invent with special emphasis on energy-saving creations and writes articles on the human phenomenon of addictions. He current hosts several Blogs, which you can locate HERE. ]

During this 1982 time frame, I was attending TSTI/Waco (which is now TSTC), majoring in Electronics Technology [ELT]. Although many two-year programs that I heard about were weak in their curiculum, TSTI was over the top, training people to become right hand designers alongside electrical engineers.

In August 1983 I graduated from TSTI/Waco.

Shortly afterward, my first technical stint was a position with Tandy Computer Assembly {click to read about my experiences there} in San Antonio, Texas. I spent several months doing component level board repair to the desktop Model IV computers that were being produced there at the time. I worked my way from board repair to the floor technician area where production testers were being built and maintained. I was assigned a project there that would take me into the Research and Development area up until the time I left. At the point in time where I left, I was developing a test routine to use the Nicolet NICE Z-80 In Circuit Emulator to replace the existing "Function Testers". I had been there one entire year.

I don't claim any foresight to the soon-to-come events, but left this company for some slightly better pay. Little did I know production on the Model IV computer was being killed at the corporate level, literally as I was walking out the door on my last day. The COCO, or COlor COmputer was coming and most of the plant would get layed off a few months later. There were some 30 to 50 employees there a year later when I visited.

I learned a great deal about the Z-80 and the hardware in this computer in this short period of time, some neat assembly language tricks, and got to sample some huge assembly software packages that the lead engineer was developing to run tests, and probably got more exposure to the different technologies that were being worked on internally than most in the plant. It was the zenith of my Z-80 training. The FORCE was with me - ha.

After that I pretty much left the Z-80 behind as I worked in the medical equipment field. I saw more than a few Z-80's inside a lot of the equipment I was working on, but not much other exposure.

JP ahead to ...
2001 when I began searching Ebay for things related to the Zilog Z-80 microprocessor. I guess it was out of sheer curiosity, I'm not sure. However, I located a bare Z-80 pcb for sale by Ron Weiss (networkrw is his seller name on Ebay, if you are interested). I decided to break down and spend the $7.00 that it took to get the bare PCB after he was kind enough to email me scans of the schematic diagrams. Later I realized I didn't have as many spare parts workable that I first thought, and went back to him for the IC's to populate the board, having prepped it with every socket I could find.

He also sold me a 2K Monitor Rom to drive the board with simplistic TTY commands accessible by tying the RS232 port to the D9 RS232 port on my home PC.

That would be the beginning of a long love affair with my Z-80 computer that I probably should have had back in the mid 1980's when I was absorbed in the work anyway.
Now I think this is called "Nostalgia", or "Obsession", whichever you prefer. Whatever...

My Z-80 box resides in an oversize 3U rack-mount cabinet with a 2x40 character LCD display and an 8-LED port display. I've gradually evolved the Monitor program to where it now operates off the 8279 keyboard and LCD display. I used the expanded memory capabilities and high current drive I/O to actuate test systems and panels at my work.

My Port-Over of the Nascom-Microsoft 8K BASIC for this board which uses floating point math is fully operational [This project took 7 months worth of lunch hours]. I ported over the initial version to run on my memory expansion board giving about 48K bytes of space. After I got it working, I created a version to run on the standard, or unmodified Space-Time Productions board.

At one point I interfaced a stepper motor out of an old 5-1/2" floppy diskette drive onto the discrete output array. It worked really well, and I wrote a few programs in both assembly and BASIC to drive it. The fastest step time it would accomplish was 1.25mSec, pretty quick but doesn't allow enough coil-on time to develop serious level of torque. Since this doesn't really correlate to any of the focal points I have been working on, I removed the motor, but attached it to a D25 connector which I can hook to my discrete output port at will. It would be a good stepping stone for someone interested in robotics. The code is included over on the software page, if you are interested.

On the hardware front: As of 2010, I've removed the memory expansion board getting it ready to swap the low page of rom with ram, and to incorporate a CF card for a hard drive. My hope is to eventually get CP/M running and available for this board.

Other irons in the fire:
I've been fascinated by Christmas lighting, and the video that made its way around this 2005 caught my eye. I've always wanted to do something a little more over-the-top than my neighbors, and I think this is the way. I recently purchased 32 opto-triacs situated in 2 each 16-module racks. I am hoping this is going to get me started in the business, but I am already aware that it is going to take more than 32 output points to make a decent light show so I'm busy designing another I/O board for my Z-80 computer (and perhaps another couple of Z-80 computers) that use standard TO-220 Triacs and DIP triac optoisolators to drive them on from TTL logic levels.

Here's a link to a really good site about this hobby:

Here's a link to an even better site for computer-controlled Christmas lighting,
and is by-and-for electronic hobbyists:
www.computerchristmas.com.

Another grand idea - There is a tremendous website about a guy who has created a 74LSxxx TTL-logic based working replica of the Apollo Lunar AGC computing system. Tons of research and schematics. I've been working with a friend of mine to create an accurate DSKY (Display / Keyboard) for the AGC, and I would like to use one of my Z-80 boards to emulate the Apollo DSKY executive.

I used some graphic tools to brush up the Space-Time Productions logo found on the schematics. Doesn't it look great? I've gotta try and recreate this in Corel Draw someday...