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Original question:

TCAN4550-Q1: After power-on, the module goes to sleep mode instead of standby mode.

TCAN4550-Q1: TCAN4550-Q1 8 Mbps CAN FD Data Phase Not Working

vishnu reddy
Prodigy 40 points

Part Number: TCAN4550-Q1

Dear Texas Instruments Support Team,

I am using the TCAN4550-Q1 CAN FD controller with a 40 MHz crystal. I am able to achieve 5 Mbps data phase successfully. However, when I configure the data phase for 8 Mbps, communication fails in PCAN View.

My current data timing configuration is:

TCANDataTiming.DataBitRatePrescaler = 1;// 8mbps

TCANDataTiming.DataTqBeforeSamplePoint = 3;

 TCANDataTiming.DataTqAfterSamplePoint = 2;

Could you please confirm:

  1. Under what hardware conditions 8 Mbps is reliably achievable?

  2. Are there specific PCB layout requirements for stable 8 Mbps operation?

  3. Are there any mopdification for software ?

 

Thank you for your support.

Best regards,
VISHNU

  • 0
    TI__Mastermind 37471 points

    Hello VISHNU,

    When trying to operate at 8 Mbps, you have no margin for error and tolerance issues because you are using the minimum number of time quanta (tq) per bit.  The wiring harness needs to be properly terminated and free of reflections.  The clock frequencies must be almost identical to avoid re-synchronization jumps that may create sampling errors.  Also the Transmitter Delay Compensation must be set correctly.  

    Make sure that you are using the exact same nominal and data bit timing configuration settings for all nodes on the bus including your PCAN Analyzer.  This includes the operating clock frequency which is a maximum of 40MHz for the TCAN4550-Q1.  You may also need to adjust the Transmitter Delay Compensation settings in register 0x1048 to make sure you aren't getting secondary sample point errors during transmission.  The clock/crystal oscillation frequency must also closely match that of the other nodes because this determines the width of a time quantum (tq) and the overall bit width.  If the clock/crystal oscillation frequency is not within the required tolerance as defined in the ISO 11898-1:2016 standard, then you will be susceptible to errors.

    The following documents may be useful for additional information:

    TCAN45xx Software User's Guide (Link)

    MCAN User's Manual (Link)

    Recommendation for the CAN FD bit-timing (Link)

    Regards,

    Jonathan