DiagBoard
To help me develop DEUCE, I created a simple diagnostic board, which includes a single step, reset, and LEDs for all the pins on the edge connector. It also has some duplicate pins, so I can easily use a Logic Analyser plus some power pins to allow connections to other stuff. The ICs, on the right, are hex buffers to minimise interference with the main board. Only the RESET and WAIT lines can change the signal at the CPU. This is a video of me powering it up in single-step mode, then doing some steps, letting it run for a while, and then back to single-step. While it is in step mode, the screen misbehaves. This happens because the software is accessing the Video RAM and locking out the VDG. The software is my little test harness which can be found on GitHub here . The design for the diag board is also on GitHub here . There are some slight differences from this version. One is changing a label on a pin, and the other is adding a PWR LED.