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TCAN4550-Q1: The SPI signal alternates with the TCAN signal

Amy Luo
Expert 6895 points
Part Number: TCAN4550-Q1
Other Parts Discussed in Thread: TCAN4550

Hi team,

Figure 1, yellow for canH signal and blue for spi ncs signal

Figure 2, yellow for the spi ncs signal and blue for the spi SCLK signal

It is thus observed that the can bus signal sends a frame after a spi signal is transmitted. As a result, the module CAN frame interval is up to 1.1 ms.

1, is this normal?

2, can the spi signal content within the frame interval time is necessary to transmit information, is it possible to reduce unnecessary content, so as to achieve the purpose of reducing the frame interval size?

3, does the module work as described above, that is, each CAN frame needs to wait for the spi message containing CAN frame contents to be transmitted before a CAN frame can be issued?

Best Regards,

Amy Luo

  • +1
    TI__Guru 53575 points

    Hi Amy,

    TCAN4550 is capable of driving and receiving CAN and SPI data simultaneously. In this case, it appears that the CAN communication is being initiated by the SPI command from the MCU. It is unclear why the MCU then waits for the end of the CAN frame to send additional SPI frames. This may be because the MCU is waiting for a interrupt pin on the TCAN4550 to change states indicating that the transmission is complete. Keep in mind that all SPI communication is initiated by the MCU, so this delay is not directly a result of the TCAN4550. 

    The TCAN4550 software user's guide includes some tips for software optimization to improve effective SPI throughputs. See Section 5 of the linked document. 

    Let me know if you have any more questions. 

    Regards, 
    Eric Schott