TCAN1042-Q1_17 Datasheet, PDF (22/40 Pages) Texas Instruments – Automotive Fault Protected CAN Transceiver with CAN FD

TCAN1042-Q1, TCAN1042V-Q1, TCAN1042H-Q1
TCAN1042HV-Q1, TCAN1042G-Q1, TCAN1042GV-Q1
TCAN1042HG-Q1, TCAN1042HGV-Q1
SLLSES9B – FEBRUARY 2016 – REVISED MAY 2017
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9.4.3.1 Remote Wake Request via Wake Up Pattern (WUP) in Standby Mode
The family offers a remote wake request feature that is used to indicate to the host micrcontroller that the bus is
active and the node should return to normal operation.
These devices use the multiple filtered dominant wake up pattern (WUP) from the ISO11898-2 (2016) to qualify
bus activity. Once a valid WUP has been received the wake request will be indicated to the micrcontroller by a
falling edge and low corresponding to a "filtered" dominant on the RXD output terminal.
The WUP consists of a filtered dominant pulse, followed by a filtered recessive pulse, and finally by a second
filtered dominant pulse. These filtered dominant, recessive, dominant pulses do not need to occur in immediate
succession. There is no timeout that will occur between filtered bits of the WUP. Once a full WUP has been
detected the device will continue to drive the RXD output low every time an additional filtered dominant signal is
received from the bus.
For a dominant or recessive signal to be considered "filtered", the bus must continually remain in that state for
more than t_{WK_FILTER}. Due to variability in the t_{WK_FILTER}, the following three scenarios can exist:
1. Bus signals that last less than t_{WK_FILTER(MIN)} will never be detected as part of a valid WUP
2. Bus signals that last more than t_{WK_FILTER(MIN)} but less than t_{WK_FILTER(MAX)} may be detected as part of a valid
WUP
3. Bus signals that last more than t_{WK_FILTER(MAX)} will always be detected as part of a valid WUP
Once the first filtered dominant signal is received, the device is now waiting on a filtered recessive signal, other
bus traffic will not reset the bus monitor. Once the filtered recessive signal is received, the monitor is now waiting
on a second filtered dominant signal, and again other bus traffic will not reset the monitor. After reception of the
full WUP, the device will transition to driving the RXD output pin low for the remainder of any dominant signal
that remains on the bus for longer than t_{WK_FILTER}.
Filtered
Dominant
Wake Up Pattern (WUP)
Waiting for
Filtered
Recessive
Filtered
Recessive
Waiting for
Filtered
Dominant
Filtered
Dominant
Bus Wake via
RXD Request
Bus
Bus V_Diff
RXD
• tWK_FILTER
• tWK_FILTER
• tWK_FILTER
Figure 15. Wake Up Pattern (WUP)
• tWK_FILTER
Filtered Dominant RXD Output
Bus Wake Via
RXD Requests
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