This is a modified version of the Arduino control software for the Core Memory Shield by Jussi Kilpelainen.
The code was modified to be more readable and therefore accessible to a wider audience. The original version used direct port manipulation via registers. This method to control an Arduino's I/O is computationally fast, but difficult to read and understand.
This version uses digitalRead()and digitalWrite() instead. Pins are explicitly addressed and manipulated, making it easier to understand, what happens in the code and which pins are used.