Identifiers¶
CANOPEN always uses identifiers with a length of 11 bits (standard frames). The number of available and allowed identifiers given by this is divided into several ranges by the pre-defined connection set. This structure is designed in a way that a maximum of 128 modules (1 NMT master and up to 127 slaves) can exist in a CANOPEN network. The list of identifiers is composed of some fix identifiers (e.g. network management identifier 0) and various functional groups where each existing node, that supports the corresponding function, is assigned to one unique identifier (e.g. Receive PDO 1 of node 3 = 512 + node number = 515). Using the pre-defined connection set therefore avoids double assignment of identifiers.
| Identifier | Function | Calculation |
|---|---|---|
| 0 | Network management (NMT) | - |
| 1…127 | not used | - |
| 128 | Synchronization (SYNC) | - |
| 129…255 | Emergency message | 128 + node ID |
| 256 | Timestamp message | - |
| 257…384 | not used | - |
| 385…511 | Transmit PDO 1 | 384 + node ID |
| 512 | not used | - |
| 513…639 | Receive PDO 1 | 512 + node ID |
| 640 | not used | - |
| 641…767 | Transmit PDO 2 | 640 + node ID |
| 768 | not used | - |
| 769…895 | Receive PDO 2 | 768 + node ID |
| 896 | not used | - |
| 897…1023 | Transmit PDO 3 | 896 + node ID |
| 1024 | not used | - |
| 1025…1151 | Receive PDO 3 | 1024 + node ID |
| 1152 | not used | - |
| 1153…1279 | Transmit PDO 4 | 1152 + node ID |
| 1280 | not used | - |
| 1281…1407 | Receive PDO 4 | 1280 + node ID |
| 1408 | not used | - |
| 1409…1535 | Transmit SDO | 1408 + node ID |
| 1536 | not used | - |
| 1537…1663 | Receive SDO | 1536 + node ID |
| 1664…1792 | not used | - |
| 1793…1919 | NMT error (node guarding, heartbeat, boot-up) | 1792 + node ID |
| 1920…2014 | not used | - |
| 2015…2031 | NMT, LMT, DBT | - |