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Original question:

TCAN1043G-Q1: TCAN1043 wake-up function enable by ESD test (ISO-10605)

TCAN1043G-Q1: STANDBY from UVSUP and SLEEP

Shinji Tsuji
Genius 14189 points
Part Number: TCAN1043G-Q1


Hi team,

I would like to distinguish the STANDBY state if it came from initial power up or if it came from SLEEP state by CAN wake up signal.

It looks WAKERQ is both applicable for initial power up and CAN bus Wake up, it cannot be used for this purpose, correct?

Could you advise how to distinguish between these 2 state transition?

It looks PWRON flag might be useful, but I don't understand the description in the datasheet below.

"nFAULT = L upon entering Silent mode from Standby, Go-to-Sleep, or Sleep mode"

Could you also explain this in other words?

regards,

  • 0
    TI__Guru 53575 points

    Hi Shinji,

    I believe the PWRON flag will be the best indicator for this. This flag will be set when the device initially powers up into Standby Mode. However, the flag state will not be indicated on the nFault pin until the device transitions from its initial mode to Silent Mode. Once in Silent Mode, the nFault pin will indicate the PWRON flag state. This flag will be cleared when the device first enters Normal Mode. 

    I hope this helps clarify the functionality of this fault. Let me know if I can explain in another way or if you have any more questions.

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Genius 14189 points

    Hi Eric,

    Is there a way to distinguish PWRON flag and WAKERQ flag in Sleep mode?

    WAKERQ flag is also shown as nFAULT=Low and is only cleared after transition to normal mode, not silent mode, correct?

    regards,  

  • 0 in reply to Shinji Tsuji
    TI__Guru 53575 points

    Hi Shinji,

    Thanks for your patience while I was away for the US holiday. 

    The WAKERQ flag will be indicated by driving the RXD pin low as well as the nFAULT pin. The WAKERQ flag will leave RXD high (or high-z depending on device/supply state). 

    Yes, these flags are only cleared on transitions to normal mode. 

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Genius 14189 points

    Hi Eric,

    Is my understanding below correct?

    WAKERQ : nFAULT = Low, RXD=Low

    PWRON : nFAULT = Low (upon transition to Silent mode), RXD=Hi-Z or High

    Table 1. in the datasheet says WAKERQ flag will be set even at initial power up as below.

    "Wake up event on CAN bus, state transition on WAKE pin, or initial power up"

    If this is the case, both nFAULT and RXD go Low upon power up to standby state and Sleep to Standby state?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Guru 53575 points

    Hi Shinji,

    Good catch, I didn't notice that both flags would be set during initial power-up. That would indeed mean that RXD would not be the best indicator for this difference. Apologies for the poor suggestion.

    Another method would be to use the Wakeup source recognition flag. This flag is set in order to distinguish where a wake source originated from - locally via the WAKE pin (LWU) or remotely from the CAN bus (WUP). Initial power-up will set this flag as a local wake-up, indicated by nFAULT = L when transitioning into normal mode. A remote wake would instead be indicated by nFAULT = H upon transitioning to normal mode.

    Will this suit your needs to distinguish between power-on and remote wake states?

    Regards,
    Eric Schott