• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 34 subscribers
  • Views 164 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCAN1048AV-Q1: question about RDX signal level

Jay wang
Expert 3221 points
Part Number: TCAN1048AV-Q1

Tool/software:

Hi expert

 i saw the following picture in our datasheet. RXD is high during "Filtered Dominant RXD Output" in the below picture.

i am thinking if Recessive signal happen in "Bus Wake via RXD Request" whether RXD should be low during  "Filtered Dominant RXD Output" ?

thanks

  • 0
    TI__Expert 3221 points

    hi expert 

    i want to add a question:

    customers want to get long duration low level. so it seems like we need to more time duration of second Filtered Dominant. so what is maximum limitation duration time of  second Filtered Dominant

  • 0 in reply to Jay wang
    TI__Guru 74282 points

    Jay,

    Jay wang said:
    i am thinking if Recessive signal happen in "Bus Wake via RXD Request" whether RXD should be low during  "Filtered Dominant RXD Output" ?

    If the device is still in Standby mode after the initial wake event, then RXD will toggle low after the bus has been dominant for tWK_FILTER 

    Jay wang said:
    customers want to get long duration low level. so it seems like we need to more time duration of second Filtered Dominant. so what is maximum limitation duration time of  second Filtered Dominant

    The maximum time is the tDTO in the datasheet. This is how long TXD can be held dominant. If the TCAN1048AV-Q1 is acting as a receiver, it can be held dominant indefinitely, it will depend on the limitation of the node transmitting at that time.

    Regards,

    Eric Hackett

  • 0 in reply to Eric Hackett
    TI__Expert 3221 points

    hi Eric

    thanks for you quick reply. i don't understand this word.

    Eric Hackett said:
    If the device is still in Standby mode after the initial wake event, then RXD will toggle low after the bus has been dominant for tWK_FILTER 

    i draw the following picture. Am i right?

  • +1 in reply to Jay wang
    TI__Guru 53575 points

    Hi Jay,

    While the transceiver is in standby mode and the WUP pattern has been detected, the RXD pin will be able to assert low to indicate when the CAN bus is in a dominant state. This dominant indicator has a filter time of tWK_FILTER - therefore the CAN bus will need to be dominant for tWK_FILTER before the RXD pin asserts low. Once this filter time is reached, the RXD pin will remain low until the CAN bus returns to a recessive level or the dominant timeout is reached (it is unlikely a DTO will occur during normal CAN communication). 

    Note that other single-channel 14-pin CAN transceivers may have slightly different behavior here where the RXD pin latches low after a WUP is detected and will remain low regardless of the state of the CAN bus. This is not typical behavior for 8-pin CAN transceivers like those that TCAN1048 is modeled after.

    Is the customer running into a problem detecting the wake up condition using the RXD pin in their application? Or are they only trying to better understand the behavior of the WAKE via RXD function of the device? 

    Regards, 
    Eric Schott