| Value | Meaning |
|---|---|
| readCoils0x01 | 01 (0x01) |
| readDiscreteInputs0x02 | 02 (0x02) |
| readHoldingRegisters0x03 | 03 (0x03) |
| readInputRegisters0x04 | 04 (0x04) |
| writeSingleCoil0x05 | 05 (0x05) |
| writeSingleRegister0x06 | 06 (0x06) |
| readExceptionStatus0x07 | 07 (0x07) Serial line only |
| diagnostics0x08 | 08 (0x08) Serial line only |
| getCommEventCounter0x0B | 11 (0x0B) Serial line only |
| writeMultipleCoils0x0F | 15 (0x0F) |
| writeMultipleRegisters0x10 | 16 (0x10) |
| readFileRecord0x14 | 20 (0x14) |
| writeFileRecord0x15 | 21 (0x15) |
| maskWriteRegister0x16 | 22 (0x16) |
| readWriteMultipleRegisters0x17 | 23 (0x17) |
| readFIFOQueue0x18 | 24 (0x18) |