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TRF7970A: Question about read IRQ Status Register with SPI interface

Alex Yu
Prodigy 40 points
Part Number: TRF7970A
Other Parts Discussed in Thread: TRF7964A

Due to trf7970a Datasheet(March 27, 2017), Section 6.10.5 Serial Interface Communication:

"the MCU must to do a dummy read to clear the reader's IRQ status register."

In both of the example project sloa213("MIFARE DESFire EV1 AES Authentication With TRF7970A"),and project sloc297c("TRF7970ABP_RFID_Reader_Demo"),

the trf79xx.c files, all read IRQ status register without a dummy byte, but reset it with a dummy byte.

Does it mean that the reading doesn't clear the register? If so, the next IRQ interrupt process would become very confusing.

  • 0
    TI__Guru*** 134695 points
    Hello,

    Thanks for highlighting this, that section actually should be removed from the datasheet, it escaped our gaze when making the updates earlier this year. The TRF7970A (and in turn, the TRF7964A as well) does not need the dummy read to clear the IRQ status register, unlike it's predecessor devices. Reading only IRQ Status alone is sufficient, which is why those code examples do that (this is also true with the full TI NFC stack as well).
  • 0 in reply to Ralph Jacobi
    Prodigy 40 points
    Hi Ralph,
    Thanks for your reply!