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Original question:

TCA6424A: I2C command to set the GPIO

TCA6424A: Interval time for I2C command

Shunsuke Nagata
Genius 12780 points
Part Number: TCA6424A

Hi,

Could you please let me know about TCA6424A?

1. Datasheet 8.4.4.1 : How long will Ack be replied after sending write command? (How long MCU should wait ACK after sending write command?)

2. Datasheet 8.4.4.2 : In the case of Write command -> Read command, is there a limit time between ACK and start? 

Regards,
Nagata.

  • 0
    Guru 296780 points

    This device conforms to the I²C specification.

    1. The TCA6424A (like almost any other I²C device) pulls SDA low at the falling edge of the eighth clock pulse. This ensures that SDA is stable when SCL is high during the ninth pulse. The TCA6424A does not do clock stretching, so you do not need to wait longer than that.

    2. No; the read command can follow immediately, and the TCA6424A does not do clock stretching.

  • 0
    TI__Guru 51815 points

    Hi Nagata,

    I can confirm what Clemens explained. The I2C interface can be thought of as a state machine which is clocked by SCL. As long as the max data rate of the device is respected, no artificial delay needs to be introduced on the SCL line or between frames (ACK and start). 

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Genius 12780 points

    For #2, Controller (MCU) will have wait before start condition. will the TCA6425A have issue?

    Regards,
    Nagata.

  • 0 in reply to Shunsuke Nagata
    TI__Guru 51815 points

    Hi Shunsuke,

    No, there will be no issue if there is a long delay between frames.

    Regards,
    Eric Schott