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TCAN1145-Q1: TCAN1145 State Machine and WUF

Tosh+
Expert 7850 points
Part Number: TCAN1145-Q1

Hello TCAN team,

While customer Astemo is checking all cases whether TCAN does not to miss the WUF, we got 3 question.

Q1) During move to Sleep mode, Does TCAN1145 never miss WUF?
　　　If there is anything case to miss WUF, let me know the timing/condition.

Q2) After enable "Selective Wake-up" and while moving from "Normal Mode" to "Sleep Mode",
　　　Where does TCAN1145 detect WUF and how to move "Standby Mode"?

Q3) When TCAN1145 receive WUF command in below section, which mode does it move to??
1) Before SPI comm(SPI Write MODE_SEL = 001)
2) During SPI comm(SPI Write MODE_SEL = 001)
3) After SPI comm(SPI Write MODE_SEL = 001)
4) During tMODE_NOM_SLP

Regards,
ti

  • 0
    TI__Mastermind 47895 points

    Hi Ti, 

    Selective wake with wake up frame (WUF) detection is active as soon as the device enters sleep mode (when configured). The device begins monitoring the bus once the transition is made. Keep in mind that any bus activity made just before this transition will be relayed to the CAN controller via the RXD pin as the receiver will still be active in any active mode (Normal, Listen). The transition to sleep mode takes place after the entire SPI command has been sent, so any activity sent before or during the SPI transaction will not be recognized by the transceiver (but will pass through the RXD pin). 

    Keep in mind that when a wake up frame is sent by a remote node, the frame is often sent repeatedly until the target node responds. In such a case that the first WUF occurs during the transition to sleep mode, the subsequent frames will be recognized by the transceiver.

    Let me know if you have any more questions.

    Regards,
    Eric Schott

  • 0
    TI__Expert 7850 points

    Hello Eric,

    Thanks for the quick reply!

    This is important explanation not to miss "WUF". Especially below comment, is the any description in the datasheet (State Diagram)?

    1) wake up frame (WUF) detection is active as soon as the device enters sleep mode

    2) transition will be relayed to the CAN controller via the RXD pin as the receiver will still be active in any active mode. 

    Regards,

    ti

  • +1 in reply to Tosh+
    TI__Mastermind 47895 points

    Hi Ti,

    From the perspective of the state machine, we can say that there is no "in-between" mode going from Normal to Sleep mode. If a WUF starts before the transition is made, the device will be in Normal mode. In this mode, the Receiver is on and the RXD pin mirrors the bus state. Thus the WUF will be partially seen by the CAN controller connected to RXD. After the transition is made, we are immediately in Sleep mode with WUF monitoring enabled. If the WUF starts at this point, the whole frame will be seen by the device and recognized as a wake event. 

    Is this sufficient for the explanation of this scenario?

    Also, while I agree that missing all WUF is a big issue, missing only one or two WUF is likely no issue as such frames are typically sent in bursts. It can take longer than a few CAN frames to fully wake a node, so it's common for several WUFs to be sent before the target node has time to respond, even when the first WUF is recognized. 

    Regards,
    Eric Schott