My first prototype used no discrete 74HCTxxx series parts, all
logic was in the CPLD. Due to several unrelated problems with
construction and the consumption of all PLD resources, I decided to
build a second prototype with using some HCT parts, this time
paying more attention to power distribution. I still believe it
would be easy to eliminate the discrete 74HCT series parts if you used
a larger PLD, like the EPM70128S. Although it might not be very cost
Here is the schematic I developed AFTER completing my prototype.
That means this schematic has not been tested. If you decide to build
this project from scratch, you should use the schematic from the
production board. If you just want a quick look at the schematic
to view a 640kB jpeg image of the schematic.