31.2.2.5 Clock Stretching

Clock stretching occurs when a device on the bus holds the SCL line low, effectively pausing communication. The client may stretch the clock to allow more time to handle data or prepare a response for the host device. A host device is not concerned with stretching as anytime it is active on the bus and not transferring data it is stretching. Any stretching done by a client is invisible to the host software and handled by the hardware that generates SCL.

The CKP bit is used to control stretching in software. Any time the CKP bit is cleared, the module will wait for the SCL line to go low and then hold it. Setting CKP will release SCL and allow more communication.