Figure 77. SPI Clock Formats when UCPHA = 0
When UCPHA=0, the slave begins to drive its MISOn output with the first data bit value when SSn
goes to active low. The first XCKn edge causes both the master and the slave to sample the data bit
value on their MISOn and MOSIn inputs, respectively.
At the second XCKn edge, the USARTn shifts the second data bit value out to the MOSIn and MISOn
outputs of the master and slave, respectively. Unlike the case of UCPHA=1, when UCPHA=0, the
slave’s SSn input must go to its inactive high level between transfers. This is because the slave can
prepare the first data bit when it detects falling edge of SSn input.