So, I'll be needing an EEPROM programmer in order to actually provide some startup software for my Z80 computer. I intend to make one using a set of shift registers, and a couple optoisolators, so that I can use any microcontroller with 8 I/O pins (7 output, 1 input), assigned as follows: Input: 1 = Data Read Output: 1 = Address/Data Write 2 = Shift 3 = ~WE 4 = ~CE 5 = ~OE 6 = ERASE/VPP (EEPROM/EPROM) 7 = Read Data The design will be as such that any microcontroller that uses either 3.3V, or 5V I/O can safely operate it. An interesting design requirement involves needing to have either 3.3/5V or 12V sent to the ~OE pin of an EEPROM, as the 5V signal is used to read from it, but the 12V is required in order to erase it. A possible solution will be to use a diode to prevent the 12V signal from feeding back to the microcontroller, and an optoisolator to gate the 12V to the same pin during an erase cycle. To obtain the 5V and 12V power rails, I will use a simple regulat...