Line rate negotiation and C&M negotiation is active all of the time.
If the link partner changes line rate, the core will fall out of CPRI hyperframe synchronization (HFN Sync).
This results in the core falling out of Operational state (1111) and into attempting L1 synchronization state (0001).
The Core will try out different rates until the receiver gets back into HFN sync.
The CPRI core stays in the operational state (1111) unless both the HDLC and Ethernet rates that the core is receiving are different to the rates that it is transmitting.
If the rates are different it will fall out of the operation state into the C&M parameter setup state (0011).
If you change the control word in Z.66.0 (for HDLC) or Z.194.0 (for Ethernet), it will cause the CPRI core to re-negotiate the C&M rate.
If both HDLC & Ethernet are used, you should change the control word of both to trigger the re-negotiation of the C&M rate.