Figure 73. Motorola Spi Frame Format, Continuous Transfers, With Spo=1 And Sph=0 - Wiznet W7500 Reference Manual

SSPCLKOUT/
SSPCLKIN
SSPFSSOUT/
SSPFSSIN
SSPTXD/
LSB
SSPRXD
nSSPOE (=0)
Figure 73.
Motorola SPI frame format, continuous transfers, with SPO=1 and SPH=0
In this configuration, during idle periods:
• the SSPCLKOUT signal is forced HIGH
• the SSPFSSOUT signal is forced HIGH
• the transmit data line SSPTXD is arbitrarily forced LOW
• the nSSPOE pad enable signal is forced HIGH, making the transmit pad high impedance
• when the PrimeCell SSP is configured as a master, the nSSPCTLOE line is driven LOW,
enabling the SSPCLKOUT pad, active-LOW enable
• when the PrimeCell SSP is configured as a slave, the nSSPCTLOE line is driven HIGH,
disabling the SSPCLKOUT pad, active-LOW enable.
If the PrimeCell SSP is enabled and there is valid data within the transmit FIFO, the start of
transmission is signified by the SSPFSSOUT master signal being driven LOW, and this causes
slave data to be immediately transferred onto the SSPRXD line of the master. The nSSPOE
line is driven LOW, enabling the master SSPTXD output pad.
One half period later, valid master data is transferred to the SSPTXD line. Now that both the
master and slave data have been set, the SSPCLKOUT master clock pin becomes LOW after
one additional half SSPCLKOUT period. This means that data is captured on the falling edges
and be propagated on the rising edges of the SSPCLKOUT signal.
In the case of a single word transmission after all bits of the data word are transferred, the
SSPFSSOUT line is returned to its idle HIGH state one SSPCLKOUT period after the last bit has
been captured.
However, in the case of continuous back-to-back transmissions, the SSPFSSOUT signal must
be pulsed HIGH between each data word transfer. This is because the slave select pin freezes
the data in its serial peripheral register and does not permit it to be altered if the SPH bit is
logic zero. Therefore, the master device must raise the SSPFSSIN pin of the slave device
between each data transfer to enable the serial peripheral data write. On completion of the
W7500 Datasheet Version1.0.0
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