TommyPROM/unlock-ben-eater-hardware/README.md

# Unlock Ben Eater Hardware

![Ben Eater EEPROM Programmer](../docs/images/ben-eater-hardware.jpg)

Utility to unlock 28C256 Software Data Protection (SDP) for the
[Ben Eater EEPROM](https://github.com/beneater/eeprom-programmer)
programmer design.  This hardware is similar to the TommyPROM hardware, but it uses
different shift register chips and different pin assignments.

To meet the 
[timing requirements of the SDP unlock](https://tomnisbet.github.io/TommyPROM/28C256-notes/), 
this code uses direct port writes
to set and read values on the data bus.  It will work with Arduino Uno and Nano hardware,
but would require changes for other platforms.

**NOTE** that this sketch **will not** work on TommyPROM hardware.  It is included here
to help people with locked chips who are using the Ben Eater design.

![Unlock timing with Ben Eater Hardware](../docs/images/ben-eater-unlock-timing.png)

The timing trace shows the tBLC for the bytes of the unlock sequence within 65us, well
within the required 150us in the datasheet.