31.2.3.2.1 Normal Clock Stretching

Following an ACK if the R/W bit is set (a read request), the client hardware will clear CKP. This allows the client time to update SSPxBUF with data to transfer to the host. If the Stretch Enable (SEN) bit is set, the client hardware will always stretch the clock after the ACK sequence. Once the client is ready; CKP is set by software and communication resumes.