In this example, the CAN ID is less important as the ID mask bit 0 is marked as disregard. The data is what must be matched. The steps below outline the required procedure to configure the device for this behavior, and then transition the device to sleep. Note that when selective wake is enabled, only the specific or desired WUF can wake the device, unless there is some type of error threshold that is hit (such as a decoding error).

Breaking down the example parameter values, the WUF ID is 0×123 or 0×122. The value written into the register does not matter which of the two is entered, since the ID mask will be used to mark bit 0 as disregard. By setting bit 0 of the ID mask to a 1, we tell the device to ignore this bit, which means it will accept a 0×122 or 0×123 ID. The CAN FD bus in this example has an arbitration and data rate of 500 kbps and 2 Mbps respectively. Since this theoretical bus is a CAN FD bus, we want to allow regular CAN FD traffic to occur while some nodes are asleep, so SW_PASSIVE is set to 1b.

A change for this example is to do some verification against the data payload. Note that data payload checking will require an exact match for the DLC, but the way a WUF data bit is checked is bit-wise OR only. For example, the bits that are set to 1 are checked against the payload and will be considered a match if any single bit (or more) match. Likewise, if a WUF data mask is set to 0×FF, then any value with a bit equal to 1 will be matched. If a WUF data mask is set to 0×00, then that particular byte is essentially ignored, and cannot be matched, not even if the received data is 0×00. This OR is applied across all configured data bytes (set by the DLC field). Table 5-4 provides an example of how to program the device for this behavior.