Single Board Computer
Technical Support Information
The following is technical information related to the Space-Time Productions Z80 single board computer, circa 1982. A number of these boards have been sold in the past on Ebay, both as bare pcb's and as kits complete with a full complement of necessary IC's and parts to get started.
The purpose of this web site is to be a forum to pass information related to this board to the community of people who own it. Feel free to use any information provided, I am also interested in posting any programs or information you wish to share.
Plus, it's just great fun!
If you wish to donate information, source code, or photos for use on this site, it will be credited to you along with my sincerest thanks.
I recently started a BLOG for my on-going progress with the Z-80 project! Entries cover software development, hardware gizmos, and other old systems. Also, in the planning stages is a PODCAST series about this and other Z-80 computers.
Click here for my BLOG.
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I'd like to extend a special Welcome! to visitors from the Retrobits Podcast.
Hope you'll drop me a line and let me know you were here, and Thanks for visiting!
Also, a big Thanks to Earl Evans for taking time to mention this site in his Podcast.
What a great show he has!
I explain everything in great detail, so be prepared to do some reading...
The Kit
The kit with main IC's, as seen in the past on Ebay
These kits were sold by Ron Weiss Electronics; his Ebay identification is networkrw if you wish to contact him.
The kit contained:
- CPU pcb
- A/D pcb
- Serial port-B expansion pcb
- Monitor Rom
- Z-80 Microprocessor
- Z-80 SIO-0
- 8253 Programmable Timer
- 8255 Programmable I/O (various quantities 1-3)
- 8279 Keyboard/Display Controller (not on all kits)
- Various components (not on all kits)
As of December 5, 2005 Mr. Weiss informs me that he has sold completely out of these boards, however he has a few A/D PCB's and RS-232 Second Serial Port boards remaining in his stock.
There are a number of ways you can configure this board, so it doesn't necessarily have to have all the Input/Output IC's. For instance, you may only need one PIO chip instead of three, and no keyboard/display interface.
There are a number of TTL gate IC's you will need for decoding, timing, and buffering. Refer to the schematic IC layout for a complete list of IC's, XTAL, resistors and capacitors also needed.
This is a really fun and versatile computer! Designed as an industrial controller, there is no CRT/video circuitry or mass storage interfaces. It does have RS-232 serial ports and a specialized Keyboard/Display adapter (8279) on board.
Since this kit is supplied only as a pcb, you pretty much have the freedom to creatively enclose this computer any way you like. It was likely designed to be installed inside one or more pieces of pre-existing equipment.
I have opted to use a 19" rack mount case for mine. I have designed and built a different front panel than the one that originally came with the case.
My Space-Time Productions Z80 SBC
My Z80 Single Board Computer consists of
- The bare pcb board.
- One each Z-80 microprocessor.
- 2716 Monitor rom.
- Three each 8255 PIO Programmable Input/Output IC's.
- One each 8279 Keyboard/Display IC.
- One each 8253 PIT(CTC) for baud rate generation.
- One each Z-80 SIO-0.
- Various TTL-LS logic IC's.
- Four each 2114 Static Rams (removed since the Memory Expansion PCB).
- Sockets for each IC (a rule of mine).
Expansions I Have Made To This Computer:
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Discrete I/O Board: Utilizes 4 each ULN2803 50V 500mA open-collector output driver IC's. Eight drivers on each IC provides 32 total Discrete Output points. I use 2 each 1K-ohm x 8 resistor pull-up packs tied to the 5V supply off the board. This gives me 16 Discrete switch inputs, which are high (logic 1) when the switch is open. I currently use this board to drive 28V "discrete input and outputs" on Avionics panels at my work desk, makes a good test-bed.
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Memory Expansion Board: Completed April 2005, this board added two 32K non-volatile static rams and capacity for 4 each 2732 roms. The memory is bank switched using jumper pins. The fourth Rom socket is jumper selectable to hold either a 6116 Static Ram or a 2732 4Kx8 Eprom.
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HD44740 LCD Display 2 x 40: I have also tied this 2x40 ASCII character display in using the 9511/12 socket at IC-17. This is an LED-backlit device which uses a negative 2Volts for biasing. $6.00 from BG Micro. I have built a special timing circuit using a 74LS175 which allows me to:
- Read and Write the HD44780 as a directly mapped standard I/O device
- Provide the -2.0Vdc bias voltage for the glass
- Display the data bytes to and from the LCD using latched LED's
See the Hardware page for details.
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Monitor Rom: I have added various features and functions to the original Monitor program, as follows:
December 2005: Rev 8.1 - Jumps the baud rate up to 38,400 for the console Serial A [reqs new xtal].
- Sets Serial B at 31,250 Baud for MIDI data.
- Has ANSI color sequences for changing text color on-the-fly with Hyperterminal.
- Initializes all devices on bootup, including the HD44780 LCD.
- Generates ROM checksums on bootup.
- Has a CP/M-like multi-device output print command.
- Has many other features - check my progress on the BLOG!
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MIDI Interface for Serial B port: See the menu for how I created an opto-isolated circuit for connecting MIDI devices. I have acquired a MOS 6581 CBM synthesizer IC, and am planning a music synthesis circuit board as a future add-in.
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Front Panel: I was able to salvage about 36 professional LED-lighted switches and 9 green and 9 red indicators (which also look exactly like the switches) off of some old equipment. They are top-quality devices and would probably have cost me about $6.00USD each new. Had new 19" rack panel milled-out by a friend. Completed the interface PCB and am in the middle of code and test. The control gained by this will give some monitor functions without a host PC, and will primarily be to interact with the MIDI and 6251 SID music synthesizer IC. See the pics on the 8279 Panel page, I think you'll like it.
Resources
These are two valuable books for use alongside your Space-Time Computer. The MCS-80 User's Manual cover takes several forms, here is an early one. You can usually find this one on Amazon. It's focus is on the 8080-8085, but there is a wealth of technical data sheets inside including the 2114 static ram, various proms, 8212 I/O port, a very in-depth data set on the 8255 PIO, 8251 UART and lots of good background info on RS232, 8253 PIT, and 8279.
The Z80 book by Zaks is a good resource for Z80 Assembly/Machine Code, teaches a lot about the fundamentals and concepts of programming, a good instruction code breakdown (there are a few errors in the book, but easy enough to locate and correct), how to handle data in tables, binary math and a lot about the workings of the Z80 signals. Also has execution times for each instruction based on a 2MHz clock (same as the Space-Time). Very handy.
If you own one of these computers, please take a moment to Email me!
I have heard from a number of Z-80 hobbyists from all over the world and enjoy the Email traffic!
This site created September 2004.
Mobile-Friendly version
November 2006.
Other information credited to its sources.
This Site is not affiliated with Space-Time Productions, Mr. M.Simon, or Mr. Ron Weiss, however I extend a grateful Thanks to those parties.
This site has a sole purpose to provide technical information, and is not intended to infringe any prior
copyrights nor to derive funds that would otherwise be the property of Microsoft, Space-Time Productions
or it affiliates, either past or present.
May the Force be with you.