8031 Trainer (Festo PLC) Evaluation board

I don’t have schematics for my Festo programming device.
I now found this Festo evaluation board on ebay. Unlike my PDP8-CPU this has an 80c31. Not sure for what PLC this is, I assume a Festo 101 (or 202).

There are many latches, input buffers and input latches. Not all connections are printed, especially not the large i/o connector.
There’s mem and i/o decoding.
From the mem decoder, A12-A15 are used. The i/o decoder uses A14-A15 and A4-A7.
There’s a program selector, but of course I don’t know the contents of the EPROM.

Below are the single i/o lines. On the far right is Start/stop.

I’m currently also writing a disassembler for my device. (90% finished)
It’s not that easy. The first 2 instructions differ from the 3rd and later ones.
The first have to check for an input.
The second can have a simple output setting, or an OR clause.
The 3rd can start with a new first condition, or have an extension depending on the 2nd one.

Probably the list of the functional units sorted by number is the easiest one and maybe stored on my EPROM that way. The complicated instructions with 2 operands are at bottom. I think it could be stored backwards. Seems easier to code.

That’s a beautiful board, and very nicely kept.