• 3WIRE
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  • Serial CLI

Recipe · Advanced · 3WIRE

How to write bytes to a 93Cxx Microwire EEPROM

Use the 3WIRE EEPROM shell to write a small test byte sequence to a 93C46, 93C56, 93C66, 93C76 or 93C86 EEPROM.

Microwire EEPROM connected to a three-wire bus.
A practical ESP32 Bit Pirate workflow based on the documented firmware commands.

Wiring View

BP CS/SK/DI/DO3WIRE pinsORGGND for x8 or V...VCC/GNDEEPROM supply a...
Generated from the wiring summary: to BP.
Step 1

Commands

Open the 3WIRE EEPROM shell, then choose Write bytes in the interactive menu after probing and backing up the chip.

Result

What it means

A readback that matches your test bytes confirms the 3WIRE pin mapping, organization mode and write-enable flow.

Troubleshooting

  • If readback is wrong, check ORG state.
  • If probe is unreliable, verify CS/SK/DI/DO mapping.
  • Do not erase production EEPROMs without a backup.

Next steps

  • Read back the written address.
  • Compare with a full dump.
  • Document chip model, organization and pinout.

93Cxx write FAQ

What should I write for a first test?

Use a tiny, recognizable pattern on a disposable chip or known-safe address, then read it back. Avoid writing production EEPROM data until the organization and backup are verified.

What does ORG select on a 93Cxx EEPROM?

ORG selects the memory organization, commonly x8 or x16 words depending on the chip and board wiring. The selected organization changes how addresses and data bytes should be interpreted.

Should I erase before every write?

Not always. Follow the shell behavior for the chip, but keep a backup and verify readback. Do not erase a useful EEPROM just to test that wiring works.

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