Friday, December 23, 2016

Building a 68000 Single Board Computer - Wirewrap Prototype

I've started assembly on a protoboard.

I am using a phenolic board with 0.1 inch hole spacing. I actually glued two boards together using Crazy Glue and some additional pieces of circuit board material for reinforcement to make a board large enough.

I've determined the locations for the ICs and inserted the wirewrap sockets. Until they are wired up, the sockets will fall out if the board is inverted, so to hold them in place I put a small dab of Gorilla Glue on one pin of each socket to hold it in place.

I also mounted the front panel switches and LEDs and some connectors. Power will connect using two binding posts. Two 6-pin headers will connect to the FTDI USB to serial adaptors for the two serial ports. A few discrete parts will be mounted on the perfboard but most will be installed into wirewrap sockets.

I installed 5 nylon standoffs, one on each corner and one in the center, to act as feet and lift the board up above the sockets.

Each IC has a 0.1 uF bypass capacitor installed next to it. There is a single large 100 uF electrolytic filter capacitor installed near the power connections.

The next steps are to wire up power to the power switch and LEDs and some of the ICs, then assemble the clock oscillator, power and pushbutton reset circuits and the microprocessor so I can get it to the same state as I had earlier on the breadboard - being able to run in freerun mode.

No comments: