ZMJC Computer

Introduction

During my MSc in Electrical and Electronic Engineering at The University of Nottingham (1992-3) we used this single boad computer for an assembly programming module. It must have been designed by one of the university staff, but I don't know 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
• 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 V9938
• Add realtime clock, eg Epson RTC7242
• Storage controller (eg FDD).

Connectors

CON1: ADC Input / DAC Output

Pin	Function	Pin	Function
1a		1b
2a		2b
3a		3b
4a		4b
5a		5b
6a		6b
7a		7b
8a		8b

CON2: Expansion Bus

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

CON3: RS232 (25 pin D-Type)

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

CON4: Power

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

Main Memory

Start	End	Function
8000H	27FFFH FFFFH 9FFFH	128 KB RAM 32 KB RAM 8 KB RAM
0000H	7FFFH	32 KB ROM

IO Ports

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

TBC

Software

TBC