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PCA9534: Clock Stretching

Jonathan Navor
Genius 9475 points
Part Number: PCA9534

Hi Experts,

We need your assistance. 

The I2C specification allows for a slave device to stretch the clock if it is still busy processing a request.  Does the PCA9534 (GPIO Expander) ever perform clock stretching? Thank you in advance for your support. 

Best regards,

Jonathan

  • +1
    Guru 317320 points

    No. As shown in figure 9-1, the I²C clock pin is only an input.

  • +1
    TI__Mastermind 48228 points

    Hi Jonathan,

    To second Clemens' point, PCA9534 SCL channel is only an input. There is no clock that the PCA9534 can generate to other downstream controllers (masters) or targets (slaves). Therefore, there is no way for the PCA9534 to pull the SCL bus LOW, i.e. output a LOW signal in order to stretch the clock. 

    The I2C specification does not technically require clock stretching as a necessary feature to meet the I2C standard. 

    Regards,

    Tyler