Some rules on how to design a CAN network. Consider reading ProblemSolvingQuestions.
The rules are general and valid for an CAN network including CanOpen and DeviceNet. Therfore look at DeviceNetCable too.
bit rate | max cable length (in m) |
1Mbit/s | 25 |
800Kbit/s | 50 |
500Kbit/s | 100 |
250Kbit/s | 250 |
125Kbit/s | 500 |
50Kbit/s | 1000 |
(Table from CiA DS 301 4.02 page 20)
If you ask for a formula? There is one rule of thumb:
cable length < 40000 Kbit/s * 1 m / BitRate? in Kbit/sBitRate? given in Kbit/s as well. Using this, results in <40m for 1Mbit/s or <320m for 125Kbit/s. In this formula a typical transceiver propagation of 25ns and a typical cable propagation of 5 ns/m is used for calculation.