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Original question:

TCAN1043-Q1: Standby mode communication

TCAN1043-Q1: Standby Mode from Initial Power ON and RXD State

Kade Hudson
Prodigy 100 points
Part Number: TCAN1043-Q1


What is the state of RXD when in standby mode upon initial power up? VCC and VIO are applied shortly after VSUP. Despite what the datasheet says (receiver should be held at logic low), RXD seems to be active when CAN bus is applied. Is this expected behavior?

  • 0
    TI__Guru 62920 points

    Kade,

    I'd expect RXD to be high in standby mode until a wake request is received, then assert low. Do you see RXD toggle repeatedly without a change of state on EN or STB (i.e., without transitioning to normal or silent modes)?

    Max

  • 0 in reply to Miguel Robertson
    Prodigy 100 points

    Hi Max,

    I failed to mention that as soon as Standby mode is entered (from power up), the EN bit goes high and nSTB stays low. From what I understand, the transceiver should still be in the Standby state as the WAKERQ has not been cleared. However, the RXD toggles when CAN traffic is present.

    According to Table 3 in the datasheet, shouldn't RXD be held low?

    Kade

  • 0 in reply to Kade Hudson
    TI__Guru 53575 points

    Hi Kade,

    When nSTB is Low, the receiver is in a low power mode and is only monitoring for wakeup. Can you please confirm that you are receiving data from the CAN bus while nSTB is Low? If you could provide scope shots, it would be helpful to get a sense of all pin states. Try switching the device into different modes using EN and nSTB to see what other states RXD seems active. 

    As Max said, when the device is in standby mode, the RXD pin will output Low if there is a wakeup event from either the CAN bus or the WAKE pin. Otherwise, RXD should be High or High Z. 

    Regards,

    Eric

  • 0 in reply to Eric Schott1
    Prodigy 100 points

    Hi Eric,

    I appreciate your response. Unfortunately, I am unable to reproduce the issue at this time... 

    Thanks again,

    -Kade