29.2.3.2.1 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.