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ADS7142: ADS7142 Clock Stretching

Farmer Jo1
Prodigy 120 points
Part Number: ADS7142

Hi,
We are currently using an ADS7142 device that connects to a Microchip dsPIC33EP128MC504 I2C channel using a MAX14850 isolator. We are running the bus at 400KHz.

I am using a Digiview DV3400 logic analyser to monitor the I2C signals on both the non isolated side (CPU) and the isolated I2C signals connected to the ADS7142.

After a number of transactions it appears that the ADS7142 device is trying to clock stretch SCK. In the attachment it looks like clock stretching is occuring on pulse 3 of byte 2.

Could you confirm if this is clock stretching?

Is it typical for the ADS7142 to clock stretch mid-way through a byte as seen in the attachment?

Also why does the clock stretching occur only very occasionally? For example, we may only see it once every 50000 transactions and other times it may occur within 100 transactions.

Regards
FarmerJo

  • 0
    TI__Mastermind 24940 points

    Hello,

    This device can clock stretch, this occurs when the device needs more time to complete the on going conversion. The device will hold the clock low until it is ready to respond.  Below is an example of when clock stretching can occur.