| 01 | Read Coil Status |
| 02 | Read Input Status |
| 03 | Read Holding Registers |
| 04 | Read Input Registers |
| 05 | Force Single Coil |
| 06 | Preset Single Register |
| 07 | Read Exception Status |
| 08 | Diagnostics (Serial Line only) |
| 09 | Program 484 |
| 10 | Poll 484 |
| 11 | Fetch Communication Event Counter (Serial Line only) |
| 12 | Fetch Communication Event Log |
| 13 | Program Controller |
| 14 | Poll Controller |
| 15 | Force Multiple Coils |
| 16 | Preset Multiple Registers |
| 17 | Report Slave ID (Serial Line only) |
| 18 | Program 884/M84 |
| 19 | Reset Comm. Link |
| 20 | Read General Reference |
| 21 | Write General Reference |
| 22 | Mask Write 4X Register |
| 23 | Read/Write 4X Registers |
| 24 | Read FIFO Queue |
| 43 | Read device identification |