Odd Software for Odd Jobs

Intel MCS-85!

Something old to tinker with … an Intel 8085 development kit from the late 70s.

2016-04-06 16.51

It only needed a little bit of TLC - the rubber feet were pretty much on their last legs (ho ho) so they were easily replaced first:

2016-04-07 12.53

Then I needed some way to power it - finally decided on some PCB-mounted screw terminals. I had to clear out some solder from the through-holes first:

2016-04-07 13.04

2016-04-07 13.11

Then the screw terminals dropped straight in - the board is powered with the +5V, with the -10V used for a teletype (TTY). I created a simple power cable with banana plugs on one end so I could run it off my lab power supply.

2016-04-07 15.25

Powered it up and pressed the RESET button … and it works!

2016-04-07 15.25_2

I entered a very simple program three-byte program from the manual (simply load a value to a register) … and that worked too!

It comes with 256 byte of RAM in an 8155 (socket A16), expandable to 512 bytes by adding a second 8155 (socket A17). The monitor program is stored in an 8355 PROM (socket A14) and an additional ROM can be added (socket A15).

In the photo below you can see some stray wires from the DB9 port in the top left over to the prototyping area on the left - the previous owner has installed an RS232 interface. I'll clean this up (one wire is broken) - it requires an additional +12V and -12V supply. But this will give access to the monitor via my Mac hopefully!

2016-04-07 15.25_3

I'm fascinated to finally make a proper attempt at learning assembly!