Z51F6412
Product Specification
PS030302-0212
P R E L I M I N A R Y
104
When UCPHA=0, the slave begins to drive its MISO output with the first data bit value when SS goes
to active low. The first XCK edge causes both the master and the slave to sample the data bit value
on their MISO and MOSI inputs, respectively. At the second XCK edge, the USART shifts the second
data bit value out to the MOSI and MISO outputs of the master and slave, respectively. Unlike the
case of UCPHA=1, when UCPHA=0, the slave’s SS 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 SS
input.
XCK
(UCPOL=1)
MISO
MOSI
XCK
(UCPOL=0)
/SS OUT
(MASTER)
BIT7
BIT0
/SS IN
(SLAVE)
BIT6
BIT1
…
…
BIT2
BIT5
BIT0
BIT7
BIT1
BIT6
SAMPLE
MSB First
LSB First
Figure 11-29 SPI Clock Formats when UCPHA=0