LM3S5R36_13 Datasheet, PDF (671/1063 Pages) Texas Instruments – LM3S5R36 Microcontroller

NRND: Not recommended for new designs.
Stellaris^® LM3S5R36 Microcontroller
Figure 14-4. Freescale SPI Format (Single Transfer) with SPO=0 and SPH=0
SSIClk
SSIFss
SSIRx
SSITx
MSB
MSB
4 to 16 bits
LSB Q
LSB
Note: Q is undefined.
Figure 14-5. Freescale SPI Format (Continuous Transfer) with SPO=0 and SPH=0
SSIClk
SSIFss
SSIRx _LSB
SSITx LSB
MSB
MSB
4 to16 bits
LSB
LSB
MSB
MSB
In this configuration, during idle periods:
■ SSIClk is forced Low
■ SSIFss is forced High
■ The transmit data line SSITx is arbitrarily forced Low
■ When the SSI is configured as a master, it enables the SSIClk pad
■ When the SSI is configured as a slave, it disables the SSIClk pad
If the SSI is enabled and valid data is in the transmit FIFO, the start of transmission is signified by
the SSIFss master signal being driven Low, causing slave data to be enabled onto the SSIRx input
line of the master. The master SSITx output pad is enabled.
One half SSIClk period later, valid master data is transferred to the SSITx pin. Once both the
master and slave data have been set, the SSIClk master clock pin goes High after one additional
half SSIClk period.
The data is now captured on the rising and propagated on the falling edges of the SSIClk signal.
In the case of a single word transmission, after all bits of the data word have been transferred, the
SSIFss line is returned to its idle High state one SSIClk period after the last bit has been captured.
However, in the case of continuous back-to-back transmissions, the SSIFss signal must be pulsed
High between each data word transfer because the slave select pin freezes the data in its serial
peripheral register and does not allow it to be altered if the SPH bit is clear. Therefore, the master
device must raise the SSIFss pin of the slave device between each data transfer to enable the
October 06, 2012
671
Texas Instruments-Production Data