| Function code | Message contents | Direction | Message ID |
| 0 | Master control message | Rx (to node) | 00h |
| 0 | Emergency | Tx (from node) | 01h–1Fh |
| 1 | Poll message | Rx (to node) | 20h |
| 1 | Process data channel 1 | Either | 21h–3Fh |
| 2 | Process data channel 2 | Either | 41h–5Fh |
| 3 | Process data channel 3 | Either | 61h–7Fh |
| 4 | Process data channel 4 | Either | 81h–9Fh |
| 5 | Service data request channel | Rx (to node) | A1h–BFh |
| 6 | Service data response channel | Tx (from node) | C1h–DFh |
| 7 | Status channel | Tx (from node) | E1h–FFh |
Table 2—Eight function codes are available for MicroMessaging message IDs. The direction column specifies whether this is a message coming from or going to the addressed node.