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TCA9539: I / O port status when sending NACK

Y.Ottey
Mastermind 6145 points

Part Number: TCA9539

Dear TI Team

Our customer wants to expand the IO port by performing I2C communication between the microcomputer (master) and TCA9539 (slave).

I have been asked by them about the behavior of the I / O port on the TCA9539 in the event of an I2C communication error.
For example, the data sheet describes the behavior when NACK is sent from TCA9539 to the microcomputer (master) as follows.

Is it okay to recognize that the I / O port is in a high impedance state when the TCA9539 sends a NACK to the master?
If not, please let me know what the I / O port will be in the above case.

Best Regards,
Y.Ottey

  • 0
    Guru 321490 points

    The I/O ports change only after a succesful write transaction (after which the TCA sends an ACK).

    Read transactions (whether successful or not) do not change the I/O ports. The NACK described above is not an error, but signals the end of the transaction.