After I received Ben Eater's 6502 Breadboard Computer for by birthday, I realized I didn't have all of the materials needed to build the kit. One of the chips need to make the computer work is the EEPROM. This is a storage device that stores the program. If I wanted to make any programs for this computer I would need a way to put the data onto the chip. One option was a $70 EEPROM Programmer. I didn't want to have to buy anything else so instead I decided to make my own. To do this I planned on using an Arduino Uno that I had. The chip has 28 pins while the Arduino Uno only has 14 digital pins (off or on) and 6 analog pins (0-5 volts). This was a problem that could easily be solved by shift registers. Shift registers generally have a clock pin and an input pin. When ever the clock pin goes high the data in the register shifts over and adds the input pin. Watch this for a full expiation.
This would allow me to use only a few pins on the Arduino but have a lot more outputs. I build up a circuit using 3 shift registers. 1 shift register for the data and 2 shift registers for the address.
The next step was to wire all of the outputs of the shift registers to the EEPROM. In theory I could now program the EEPROM. In actuality it didn't work. I spend hours trying to find the problem and was never successful. Looking back it was probably having all of the LEDs hooked up to the output lines because this could mess up the input voltages on the EEPROM. I ended up putting this project aside when I got an EEPROM programmer.
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