ZMJC Computer
Introduction
During my MSc in Electrical and Electronic Engineering at The University of Nottingham (1992-3) we used this single board computer for an assembly language programming module. It must have been designed by one of the university staff, but I can't remember who; it is just labelled "© 1991 MJC". Hence, I will refer to this as the ZMJC Computer. I lost the schematic many years ago.
Key features:
- Z80180 CPU (Z80 compatible) running at 6 MHz (12 MHz crystal)
- 256 KB EPROM
- 8 KB RAM (32 KB or 128 KB options)
- 8 bit switch input
- 8 bit LED output
- RS232 option
- ZN559 DAC option
- AD7828 or ACD0809 ADC option
It is intended that this page will ultimately document the schematic and repoducible PCB layout after I have reverse engineered it.
Long-term extensions:
- Expand to 1 MB RAM
- Add sound, eg Y8950
- Voice synthesiser, eg TMS5220
- Add video out, eg TMS9918, V9938
- Add realtime clock, eg Epson RTC7242
- Storage controller (eg FDD with GM82C765B controller).
Connectors
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1a | 1b | ||
| 2a | 2b | ||
| 3a | 3b | ||
| 4a | 4b | ||
| 5a | 5b | ||
| 6a | 6b | ||
| 7a | 7b | ||
| 8a | 8b |
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1a | 1b | ||
| 2a | 2b | ||
| 3a | 3b | ||
| 4a | 4b | ||
| 5a | 5b | ||
| 6a | 6b | ||
| 7a | 7b | ||
| 8a | 8b | ||
| 9a | 9b | ||
| 10a | 10b | ||
| 11a | 11b | ||
| 12a | 12b | ||
| 13a | 13b | ||
| 14a | 14b | ||
| 15a | 15b | ||
| 16a | 16b | ||
| 17a | 17b | ||
| 18a | 18b | ||
| 19a | 19b | ||
| 20a | 20b | ||
| 21a | 21b | ||
| 22a | 22b | ||
| 23a | 23b | ||
| 24a | 24b | ||
| 25a | 25b |
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1a | 1b | ||
| 2a | 2b | ||
| 3a | 3b | ||
| 4a | 4b | ||
| 5a | 5b | ||
| 6a | 6b | ||
| 7a | 7b | ||
| 8a | 8b | ||
| 9a | 9b | ||
| 10a | 10b | ||
| 11a | 11b | ||
| 12a | 12b | ||
| 13a | 13b |
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1a | +5 V DC | 1a | +5 V DC |
| 2a | 0 V | 2b | 0 V |
| 3a | 3b | ||
| 4a | 4b | ||
| 5a | 5b | ||
| 6a | 6b | ||
| 7a | 7b | ||
| 8a | 8b |
Jumpers:
- RESET: Close to reset
- RAMSIZE: 8 KB or 32 KB/128 KB
Memory Map
| Start | End | Function |
|---|---|---|
| 8000H | 27FFFH FFFFH 9FFFH |
128 KB RAM 32 KB RAM 8 KB RAM |
| 0000H | 7FFFH | 32 KB ROM |
| Port | Function |
|---|---|
| 90H | Switch Input |
| 88H | DAC Output |
| 87H | ADC Input 8 |
| 86H | ADC Input 7 |
| 85H | ADC Input 6 |
| 84H | ADC Input 5 |
| 83H | ADC Input 4 |
| 82H | ADC Input 3 |
| 81H | ADC Input 2 |
| 80H | ADC Input 1 |
Circuit Description
Software
TBC