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Eighties telco technology reverse engineering.
Eagle VHDL
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This repository contains all the knowledge I could gather about a vintage, 80-ies TelCo card marked CARD0117 model TN-135:

Complimentary commentary can be found on my blog.

Notable observations


The card appears to have been modded at one point. It's factory marked as TN-104 (despite the actual PCB being marked TN64), but that has been crossed-out and marked TN-135 with a faint marker. The aboundance of blue mod-wires seems to support this.

Ok guys, I think the EEPROM works, let's program this thing.

Top ROM chip's contents are amusing:

00000ea0: 0a0d 5448 4520 5155 4943 4b20 4252 4f57  ..THE QUICK BROW
00000eb0: 4e20 424f 5820 4a55 4d50 5320 4f56 4552  N BOX JUMPS OVER
00000ec0: 2054 4845 204c 415a 5920 4652 4f47 0a0d   THE LAZY FROG..

Just use the leftovers, she'll be a'ight.

Some logic gates on the board are used in a sub-optimal way (either combined into another logic gate, or with signals travelling to the other side of the PCB and back). Most likely due to space/money constraints.


I find the idea of Full-Full-Stack Development (FE downto metal) appealing, so I've started making some lateral movements towards it. Also, computer archeology, what's not to like?

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