The TCAN1472-Q1 supports a remote wake-up request that is used to indicate to the host controller that the bus is active and the node should return to normal operation.

The device uses the multiple filtered dominant wake-up pattern (WUP) from the ISO 11898-2:2024 standard to qualify bus activity. Once a valid WUP has been received, the wake request is indicated to the controller by a falling edge and low period corresponding to a filtered dominant on the RXD output of the TCAN1472-Q1.

The Wake-Up Pattern (WUP) comprises four pulses: a filtered dominant, followed by a filtered recessive, then another filtered dominant, and finally another filtered recessive. After the first filtered dominant pulse, the bus monitor waits for a filtered recessive without being reset by other bus traffic and does the same until second filtered recessive pulse. Upon receiving the second filtered recessive pulse, WUP is recognized. RXD is set permanently low upon subsequent dominant pulses.

For a dominant or recessive to be considered filtered, the bus must be in that state for more than the t_{WK_FILTER} time. Due to variability in t_{WK_FILTER} the following scenarios are applicable. Bus state times less than t_{WK_FILTER(MIN)} are never detected as part of a WUP, and therefore, no wake request is generated. Bus state times between t_{WK_FILTER(MIN)} and t_{WK_FILTER(MAX)} may be detected as part of a WUP and a wake-up request may be generated. Bus state times greater than t_{WK_FILTER(MAX)} are always detected as part of a WUP, and thus a wake request is always generated. See Figure 7-7 for the timing diagram of the wake-up pattern.

The pattern and t_{WK_FILTER} time used for the WUP prevents noise and bus stuck dominant faults from causing false wake-up requests while allowing any valid message to initiate a wake-up request.

The ISO 11898-2:2024 standard has defined wakeup filter time to enable 1Mbps arbitration.

For an additional layer of robustness and to prevent false wake-ups, the device implements a wake-up timeout feature. For a remote wake-up event to successfully occur, the entire WUP must be received within the timeout value t ≤ t_{WK_TIMEOUT}. If not, the internal logic is reset and the transceiver remains in the current state without waking up. The full pattern must then be transmitted again, conforming to the constraints mentioned in this section. See Figure 7-7 for the timing diagram of the wake-up pattern with wake timeout feature.

Figure 7-7 Wake-Up Pattern (WUP) with t_{WK_TIMEOUT}