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

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# Unlock Ben Eater Hardware
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![Ben Eater EEPROM Programmer](../docs/_docs/images/ben-eater-hardware.jpg)
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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
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[timing requirements of the SDP unlock](https://tomnisbet.github.io/TommyPROM/docs/28C256-notes),
this code uses direct port writes
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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.
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**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.
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![Unlock timing with Ben Eater Hardware](../docs/_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.