25.3.2.2.2 Normal Mode
In Normal mode, the SPI peripheral will remain idle as long as the SS pin is driven high. In this state, the software may update the contents of the SPIn.DATA register, but the data will not be shifted out by incoming clock pulses on the SCK pin until the SS pin is driven low. If SS is driven low, the slave will start to shift out data on the first SCK clock pulse. When one byte has been completely shifted, the SPI Interrupt flag (IF) in SPIn.INTFLAGS is set.
The user application may continue placing new data to be sent into the SPIn.DATA register before reading the incoming data. New bytes to be sent cannot be written to SPIn.DATA before the entire transfer has completed. A premature write will be ignored, and the hardware will set the Write Collision Flag (WRCOL in SPIn.INTFLAGS).
When SS is driven high, the SPI logic is halted, and the SPI slave will not receive any new data. Any partially received packet in the shift register will be lost.
