EEPROM Protocol
Command format, byte 0 bitfield, and address spaces for EEPROM access on the Lucas 5AS.
Setup: 5-baud init with address 0x9D (replies 0x55 0x83 0xF7).
Address spaces:
- EPROM/RAM:
0x00–0xFF - EEPROM:
0x100–0x1FF
A command is always 4 bytes. Write size is always 1; read size is set in byte 0.
| Index | Field | How |
|---|---|---|
| 0 | Bitfield (see below) | — |
| 1 | Address bits 8:1 | address >> 1 |
| 2 | Value to write | 0x00 to read |
| 3 | Terminator | always 0xAA |
Byte 0 bitfield
| Bit | Field | How |
|---|---|---|
| 0 | Address bit 0 | LSB of the target address |
| 1–3 | Read size | value 0–7, reply length = value + 1 (1–8 bytes) |
| 4 | — | unused |
| 5 | Write flag | 1 = write, 0 = read |
| 6 | EEPROM select | 1 if address ≥ 0x100, else 0 |
| 7 | — | unused |
Full address: (byte1 << 1) | (byte0 & 1).