29.5.7 Clock Synchronization and the CKP Bit

Any time the CKP bit is cleared, the module will wait for the SCL line to go low and then hold it. However, clearing the CKP bit will not assert the SCL output low until the SCL output is already sampled low. Therefore, the CKP bit will not assert the SCL line until an external I²C host device has already asserted the SCL line. The SCL output will remain low until the CKP bit is set and all other devices on the I²C bus have released SCL. This ensures that a write to the CKP bit will not violate the minimum high time requirement for SCL (see the figure below).