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MPC5644A: DSPI_MCR[SMPL_PT] cannot be used with CPHA=1?

Question asked by Etienne Alepins on Jan 30, 2015
Latest reply on Feb 6, 2015 by Etienne Alepins

Hi,

 

The MPC5644A RM Rev 6 "Functional description" only talks about SMPL_PT field in the "30.9.6.3 Modified SPI/DSI transfer format (MTFE = 1, CPHA = 0)" chapter, No word about it in "30.9.6.4 Modified SPI/DSI transfer format (MTFE = 1, CPHA = 1)". However, according to its description in the MCR register, it is not tied to any particular CPHA setting.

 

It would be useful for us to delay by 1 or 2 system clocks the sample point of the DSPI SIN (we are in master mode, CPHA=1, CPOL=0). Can we interpreet the Data Setup Time for Inputs (tSUI) of the datasheet (Rev. 7) of 20 ns (for 5V input) as being the time between the SIN data being value and the sample point? If so, then the requirement would become 20 - 2*1/150MHz = 7 ns between data valid and clock rising edge.

 

Thanks,

Étienne

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