Quite often I need to be able to manually toggle the input pins on a PAL chip so I can observe its behavior. Ive needed to use this method to reverse several registered devices and also the Amstrad 6128 HAL chip that used latches.
Up till now Ive either used a program written on the Boardmaster 4000 or an old circuit board I made up with switches and LED’s.

I recently got my hands on an Arduino MEGA 2560 which is a really nice bit of kit so as my first project I thought I would implement my pin toggler on this device.
After several days of learning Ive finally arrived at something im happy with using.

Right now its all on a proto board but I have just finished making a “shield” for this.

Its controlled via the terminal window (I use Putty) and also gives its output via the same terminal. It also detects the configuration of all the programmable I/O’s and sets up accordingly.

The code also fully supports switching between 20 and 24 pin devices so it just needs a link to determine which device you are using.
Its a simple concept but took a surprising amount of coding to implement.
Loving the Arduino and will be looking at doing a lot more with it in the future.