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Initialization of RTC PCA21125

Question asked by Raghu Rajappa on Jul 3, 2019
Latest reply on Jul 9, 2019 by Jose Alberto Reyes Morales


I am trying to interface the PCA21125 RTC with the MPC5745R, through SPI. I find it difficult to comprehend the initialization part of the documentation for the RTC. 

Could you please clarify if my understanding is correct? Steps for initialising the RTC.

1. Initialize the SPI as MASter

2. (Not sure part) Set the POR_OVRD bit. I would assume that the POR_OVRD bit would be set if a reset had occured already. I don't completely understand the connection between the POR_OVRD bit and the RF bit (in the seconds reigster). 

3. If the POR_OVRD bit is set, this means the RTC is available for configuration. So then write the desired time registers. Then clear the POR_OVRD bit. 


Is this workflow correct? Also I would like to understand if the EXT_TEST bit should be set for configuration? I understand/think that it is possible to re-configure/initialize when the RTC is running in normal mode itself. but just clarifying.