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TRF7960A: IRQ 0XC0 Issue

Gust Zhang
Expert 5801 points
Part Number: TRF7960A
Other Parts Discussed in Thread: TRF7960

Hi Team,

My customer has occurred this phenomenon.

1. When the tag is not close, the PCD sends a REQA command to the PICC, the chip IRQ pin goes into an interrupt, reads the IRQ register value is 0x80, and TX complete.

2.When the tag is near, the PCD sends a REQA command to the PICC, the chip IRQ pin goes into an interrupt, reads the IRQ register value is 0xC0, TX error.

For this phenomenon, I see the app note, it explains that the interrupt for the TX complete event (IRQ status = 0x80) is not serviced quickly enough. This can either be an issue with priority of the interrupt or MCU clock speed. In my customer's application, the MCU clock speed is 48Mhz. They use the timer interrupt and IRQ interrupt, which interrupt is the first priority?

Do you have any suggestions to debug this issue? Thanks a lot and look forward to a reply.

BR

Gust

  • 0
    TI__Mastermind 18265 points

    Hello Gust,

    from my knowledge this problem only occurs when the TX interrupt is not serviced fast enough. If it is a reproduceable behavior that this is only caused by the distance between the PICC and the PCD it must have a different reason. The RX IRQ flag is only set when a RX SOF is detected. The only reason I can think of, would be noise but even that is unlikely.

    Foe debugging I would suggest setting a GPIO pin in the ISR and measure with an oscilloscope the RF and trigger on that pin signal to measure the time from the last modulated PCD bit (end of TX) to the occurrence of this signal. This should help to judge if the ISR is started fast enough.

    Best Regards,

    Helfried  

  • 0 in reply to Helfried Vollbrecht
    TI__Expert 5801 points

    Hi Helfried,

    Thanks for your reply. One more question, they use the timer interrupt and IRQ interrupt, which interrupt is the first priority?

    Best Regards,

    Gust

  • 0 in reply to Gust Zhang
    TI__Mastermind 18265 points

    Hello Gust,

    because I don't know what the timer interrupt is for and how critical it is, from my standpoint the TRF7960 IRQ must serviced first. As long as the TRF7960 TX IRQ can be handled fast enough to reset the FIFO before the RX starts the system should work. 

    Best Regards,

    Helfried