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TCA9539: Do i need to read the status two times to clear the INT pin if two inputs are triggered at the same time ?

PYTsai
Genius 11645 points
Part Number: TCA9539

Hi 

 Do i need to read the status two times to clear the INT pin if two inputs are triggered at the same time ?

Thanks!

  • 0
    Guru 317060 points

    There is no internal queue of events. For each pin, there are two bits of state: the value when the port was read the last time, and the current value. The interrupt is active as long as the two bits are different.

    Reading the port (or the input value going back to the old value) clears the interrupt.

  • 0 in reply to Clemens Ladisch
    TI__Genius 11645 points

    Hi 

    From the datasheet, each pin I only see 1 status bit. Which register is for value read last time, and which register is for the current value ? thanks!

  • 0 in reply to PYTsai
    Guru 317060 points

    The bit is stored in the flip-flop labelled "Input Port Register". The old value cannot be read; the flip-flop is updated whenever you are reading it through I²C.

  • 0 in reply to PYTsai
    TI__Mastermind 47888 points

    Hi PYTsai,

    Two inputs changing state will only flag 1 interrupt since there is only one interrupt pin. 1 read of the input port register clear the interrupt. There is no internal que or buffer that stacks interrupts. 

    There is not a register for storing the previously recorded value. I believe any sort of memory would have to be done via software. 

    Regards,

    Tyler