![Texas Instruments TM4C1294NCPDT Скачать руководство пользователя страница 1239](http://html1.mh-extra.com/html/texas-instruments/tm4c1294ncpdt/tm4c1294ncpdt_datasheet_10955931239.webp)
If the QSSI is enabled and valid data is in the transmit FIFO, the start of transmission is signified
by the
SSInFss
master signal being driven Low, causing slave data to be immediately transferred
onto the
SSInDAT1/SSInRX
line of the master. The master
SSInDAT0/SSInTX
output pad is
enabled.
One-half period later, valid master data is transferred to the
SSInDAT0/SSInTX
line. Once both
the master and slave data have been set, the
SSInClk
master clock pin becomes Low after one
additional half
SSInClk
period, meaning that data is captured on the falling edges and propagated
on the rising edges of the
SSInClk
signal.
In the case of a single word transmission, after all bits of the data word are transferred, the
SSInFss
line is returned to its idle High state one
SSInClk
period after the last bit has been captured.
However, in the case of continuous back-to-back transmissions, the
SSInFss
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
SSInFss
pin of the slave device between each data transfer to enable the
serial peripheral data write. On completion of the continuous transfer, the
SSInFss
pin is returned
to its idle state one
SSInClk
period after the last bit has been captured.
17.3.7.6
Freescale SPI Frame Format with SPO=1 and SPH=1
The transfer signal sequence for Freescale SPI format with
SPO
=1 and
SPH
=1 is shown in Figure
17-9 on page 1239, which covers both single and continuous transfers.
Note:
This Freescale SPI frame format configuration is only available when operating in Legacy
SSI mode of operation.
Figure 17-9. Freescale SPI Frame Format with SPO=1 and SPH=1
SSInClk
SSInFss
SSInRx
SSInTx
Q
MSB
MSB
LSB
LSB
4 to 16 bits
Q
Note:
Q is undefined.
In this configuration, during idle periods:
■
SSInClk
is forced High
■
SSInFss
is forced High
■ The transmit data line
SSInDAT0/SSInTX
is tristated
■ When the QSSI is configured as a master, it enables the
SSInClk
pad
■ When the QSSI is configured as a slave, it disables the
SSInClk
pad
1239
June 18, 2014
Texas Instruments-Production Data
Tiva
™
TM4C1294NCPDT Microcontroller