Ramesh Hanchinal, R&D Engineer at Synopsys and Member of MIPI UniPro Working Group contributed the write up below, describing common question by designers using UniPro about power mode change implementation.
Power Mode Change defined in specification
The Local initiates Power mode change by transmitting the PACP_PWR_req packet. It waits for the reception of PACP_PWR_cnf packet. Once the PACP_PWR_cnf is received, local configures the local MPHY for new settings and closes its transmit burst.
The Local starts the PACP_REQUEST_TIMER with value PA_PACPReqEoBTimeout. This is to wait for reception of EoB. If the Remote PA Layer does not close the burst within this period, the Local PA Layer shall abort the Power Mode request and pass PA_LM_PWR_MODE_CHANGED.ind(PWR_FATAL_ERROR) to the DME. The DME in-turn issues FATAL ERROR to the application layer. If Local receives EoB before timer expiry, then Power Mode Change process completes successfully.
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