CANopen data link layer
CANopen is based on the data link layer CAN, standardized in ISO 11898-1. Although most addressing schemata are based on the base frame format, CANopen supports the extended frame format as well. Up to CANopen version CiA 301 V4.2, CANopen supported Classical CAN only. Since version CiA 301 V5.0, CANopen is based on CAN FD.
CANopen bit timing
The table below illustrates the CANopen bit timing, the resulting maximum network length, and the maximum unterminated cable drop lengths. All CANopen devices must at least support one of the defined bit-rates. Optionally, a CANopen device may support further bit-rates. The location of the sample point must be as close as possible to 87,5 % of the bit time.
CANopen bit timing table
| Bit-Rate | Bus length | Max. stub length | Accumulated stub length |
|---|---|---|---|
| 1 Mbit/s | 25 m | 1,5 m | 7,5 m |
| 800 kbit/s | 50 m | 2,5 m | 12,5 m |
| 500 kbit/s | 100 m | 5,5 m | 27,5 m |
| 250 kbit/s | 250 m | 11 m | 55 m |
| 125 kbit/s | 500 m | 22 m | 110 m |
| 50 kbit/s | 1000 m | 55 m | 275 m |
| 20 kbit/s | 2500 m | 137,5 m | 687,5 m |
| 10 kbit/s | 5000 m | 275 m | 1375 m |
CANopen physical layer
CANopen assumes a physical layer according to ISO 11898-2. The pinning for various "CANopen connectors" is provided in CiA 106. Environmental requirements to the intended application field may demand deviations from ISO 11898-2. Therefore, CANopen is open to other physical layer options. In case other physical layer options are used, the resulting CANopen device is not interoperable in most CANopen applications.