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TCAN4550-Q1: What is the sequence of reading data and nINT pin gives the signal

Zirui Su
Expert 5340 points
Part Number: TCAN4550-Q1
Other Parts Discussed in Thread: TCAN4550

Hi

I would like to ask a question that what is the sequence of reading data and nINT shows an interrupt?

In another way to say that, the nINT first gives the interrupt signal then I read the data or after I read data the nINT gives an interrupt signal?

When I do not use the function of reading data in software, although the data will transfer to TCAN4550, but the nINT pin will not generate an interrupt; When I using the function of reading data in software, nINT will generate an interrupt, how to explain that? Thank you!

  • 0
    TI__Mastermind 47895 points

    Hi Zirui,

    The nINT pin on TCAN4550 is used to reflect all interrupt states of the device. When this pin asserts low, it means that one of the interrupt flags has been set. This indicates to the MCU that the interrupt register should be read in order to identify the nature of the interrupt. In the case that the interrupt is caused by a new CAN message (mcan interrupt), the MCU can act accordingly and read the message data, release the FIFO (if necessary), and clear the corresponding interrupt. 

    In general, the nINT pin asserting indicates that the MCU may need to take some action. A new CAN message, fault condition, or error are all examples of things that may cause this pin to assert. Because sending data does not require MCU action (after initial request to send), transmitting buffer/FIFO contents should not assert nINT. If it appears that this is the case, it's likely because some error occured during the attempt to transmit. To identify the error, the interrupt registers should be read and action taken accordingly. 

    Let me know if this helps and if you have any more questions.

    Regards,
    Eric Schott

  • 0
    TI__Expert 5340 points

    Hi Eric

    Thanks for your clear explanation. I would like to know if the nINT pin active low is according to new data come, what if I do not clear the interrupt and continue to transmit the data, the nINT will keep active low until MCU clears it right?

  • 0 in reply to Zirui Su
    TI__Mastermind 47895 points

    Hi Zirui,

    Yes, the nINT pin will stay asserted until the interrupts have been cleared by the MCU. This is true even if other transactions occur with the MCU such as sending data. 

    Regards,
    Eric Schott