E & L MMD1 8080 trainer board

From: Glenn Roberts <groberts_at_mitre.org>
Date: Fri Apr 10 05:57:40 1998

this sounds exactly like an 8080 trainer i've got. unfortunately it is
packed away now but i will be getting to it next week and can give you more
information then.

it does indeed expect a 2708 eprom in one of the sockets and yes I can give
you the source code for KEX (Keyboard Executive). I can also tell you the
correct labeling for the keys.

if this is what i'm thinking it is it was described in the book "8080
Bugbook" and also in an article in one of the electronics hobbyist
magazines, probably Radio Electronics in the mid 70's.

I'll post more information when i get at my unit.

- glenn


> -----Original Message-----
> From: CLASSICCMP-owner_at_u.washington.edu
> [mailto:CLASSICCMP-owner_at_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
>
>
Received on Fri Apr 10 1998 - 05:57:40 BST