ROM Test

Earlier in the CPU NOP Test we used a breadboard that pulled the Data Bus to ground (logic 0) via 4.7K termination resistors. This had the effect of putting only 0x00 or NOPs on the Data Bus.

To test our EEPROM, we've programmed it with nothing but NOP commands -  0x00 machine code commands.

We'll know the ROM is working properly if we can see the Program Counter/Address Bus increment from 0 towards 64k (65,535).

To program the EEPROM, you'll need to either buy a professional USB-based chip programmer, or build an Arduino Nano-based EEPROM Programmer. Eventually you will want to buy the pro rig.

Here is the video you'll need to watch, possibly more than once, to understand how the Arduino Nano-based EEPROM Programmer works and how to build it: Build an EEPROM Programmer

Here is the link to the Arduino program for the Arduino Nano-based EEPROM Programmer you'll need in order to program the ROM to perform only NOPs. You will have to replace line 61 with line 56 such that it begins with "byte data[]".

Video: Z80 system executing a ROM test

Clicking on the thumbnail gif above will provide a full-size video (49.6MB, .mp4 format)