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Problem with PCA9535 interrupt reset ?

Discussion in 'Embedded' started by abeaujean, Jan 18, 2008.

  1. abeaujean

    abeaujean Guest

    Hello there,

    We are currently using the NXP PCA9535 components in a set of 4, all
    of course wired with different hardware addresses.

    Out of the 4 components, 3 are used in output mode only (addresses 0
    to 2), 1 in input mode only (address 3).

    The interrupt line goes active as expected on the "input" PCA9535
    (address 3) when a change occurs on one or more of the input lines to
    the chip.

    The "output only" components (0 to 2) were also actually read/written
    back to perform a read modify/write back operation on the output port

    AND believe it or not, the interrupt line of chip n° 3 IS reset when
    reading chip 0 for instance.

    Captures made on a state analyzer indicate clearly that the components
    are correctly driven for write and read sequences, and that the INT/
    is really reset at the end of the reading of ANOTHER chip than the one
    activating the interrupt.

    It looks as if the chip did not care about verifying if the address in
    the first byte received for the read effectively matches its own hard
    wired address !!!

    Otherwise said, any read on any address would reset the Interrupt
    request ???

    Help. If our conclusions are correct, this is enormous... Hope we are

    A. Beaujean
    abeaujean, Jan 18, 2008
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