8 CAN BWRR

The next wake up method is CAN Bus Wake Receive Request (BWRR), which is found in most CAN compliant transceivers and SBCs. This method can be used to wake both the SBC and the integrated CAN transceiver. If you are trying to activate the SBC, the SBC must be in sleep mode and the CAN transceiver must be wake capable. If the SBC is not in sleep mode, but in standby or normal mode, the CAN transceiver can be woken up through a BWRR as long as the transceiver is wake capable. A BWRR is initiated by a Wake-Up Pattern (WUP) which consists of a filtered dominant bit, followed by a filtered recessive bit, and ending with a filtered dominant bit again. The filter bits in the WUP are going to be longer than a standard bit length in a CAN network so communication can happen in-between WUP pulses and the WUP can still be considered valid.

Figure 8-1 CAN BWRR Diagram (TCAN28xx and TCAN24xx Families)