-----Original Message----- From: CLASSICCMP-owner(a)u.washington.edu [mailto:CLASSICCMP-owner@u.washington.edu]On Behalf Of Tony Duell Sent: Monday, April 06, 1998 4:07 PM To: Discussion re-collecting of classic computers Subject: E & L MMD1 8080 trainer board I picked up a few new toys at a radio rally (hamfest) yesterday, and while I've got docs on some of them, others I know nothing about so I'll be asking here as and when I start looking at them. The first is an 8080 trainer/demo board made by E&J Instruments Incorportated, 61 1st street, Derby, Conn. It's a sloping-top metal case - the top is a large PCB. Inside there's a power transformer and what's obviously a PSU regulator board. On the top PCB there are 4 PSU output terminals (Gnd, +5, +12, -12) and the following areas marked off by white silk-screen Voltage regulator (2-terminal components only - -5V supply?) Clock (8224 + xtal) Control logic (4 TTL chips) The 8080 CPU in a Textool ZIF socket. If it makes any difference, it's an NEC chip Bus Drivers (2 off 8216) Memory Decoder ('LS05, 'LS155) Memory (4 off 2114 RAM, 24 pin DIP socket, 24 pin Textool ZIF socket) I/O decoder (3 TTL chips, including an 'L42) Buffer (4 off '04). Port 0-2. 3 areas, each containing 2 off '75 latch, 8 leds, 8 resistors. Keyboard encoder (4 TTL chips) Below the keyboard encoder there's a 16 key keypad. Keys are 0-7, H, L, G, S, Reset, A, B, missing label There's also one of those solderless plugblock breadboards. Some of the strips at one end of this are connected to the 8080 bus (A0-A7, D0-D7, control lines). There are also little sockets for each of the output port lines, some more near the I/O decoder 'L42 (port select signals?) and a few more dotted about the board (halt, M1, reset, etc) Does anyone recognise this board. I assume there should have been an EPROM, probably a 2708, in one of the 24 pin sockets. If anyone has this, I'd love a hex dump of it. Also, what should the missing key be labelled? I could trace out the schematics and write a monitor program for it - in fact I may have to, but if anyone knows this unit it could save me a lot of work. -tony