LM3S6753 Datasheet, PDF (365/625 Pages) Texas Instruments – Stellaris LM3S6753 Microcontroller

Stellaris® LM3S6753 Microcontroller
For continuous back-to-back transfers, the SSIFss pin is held Low between successive data words
and termination is the same as that of the single word transfer.
14.2.4.5
Freescale SPI Frame Format with SPO=1 and SPH=0
Single and continuous transmission signal sequences for Freescale SPI format with SPO=1 and
SPH=0 are shown in Figure 14-7 on page 365 and Figure 14-8 on page 365.
Figure 14-7. Freescale SPI Frame Format (Single Transfer) with SPO=1 and SPH=0
SSIClk
SSIFss
SSIRx
SSITx
MSB
MSB
4 to 16 bits
LSB
Q
LSB
Note: Q is undefined.
Figure 14-8. Freescale SPI Frame Format (Continuous Transfer) with SPO=1 and SPH=0
SSIClk
SSIFss
SSITx/SSIRx _LSB
MSB
LSB
4 to 16 bits
MSB
In this configuration, during idle periods:
■ SSIClk is forced High
■ 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 there is valid data within the transmit FIFO, the start of transmission is
signified by the SSIFss master signal being driven Low, which causes slave data to be immediately
transferred onto the SSIRx line of the master. The master SSITx output pad is enabled.
One half period later, valid master data is transferred to the SSITx line. Now that both the master
and slave data have been set, the SSIClk master clock pin becomes Low after one further half
SSIClk period. This means that data is captured on the falling edges and propagated on the rising
edges of the SSIClk signal.
In the case of a single word transmission, after all bits of the data word are transferred, the SSIFss
line is returned to its idle High state one SSIClk period after the last bit has been captured.
April 05, 2010
365
Texas Instruments-Production Data