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How is the first byte transmitted in the SPI protocol?

Question asked by M K on Oct 24, 2017
Latest reply on Oct 24, 2017 by M K



I'm new to embedded electronics, and have started learning by using the STM32F407VG discovery board.  Overall, I think I understand the SPI protocol, but there are a few things that I'm not understanding fully with regards to data transmission.


Full Duplex TX/RX by Master (SPI Protocol)


As per the graph above, the first byte (0xF1) is transmitted in the time of one bit (and one clock cycle).  The other bytes (0xF2 and 0xF3) are transmitted into the TX buffer in the time of one byte. Why is this?


The RXNE flag is issued before the time of the eight bit in 0xF1, and is up only for a short period of time.  Does all of the data RX'ing of the first bit happen in that short period of time?


There is something I'm not understanding clearly enough about the timing of these events.  Please explain, and thank you in advance.