SSInClk
SSInFss
SSInTx/SSInRx
MSB
LSB
LSB
4 to 16 bits
MSB
SSInClk
SSInFss
SSInRx
SSInTx
Q
LSB
LSB
MSB
MSB
4 to 16 bits
Functional Description
1532
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Quad Synchronous Serial Interface (QSSI)
•
SSInClk is forced low
•
SSInFss is forced high
•
The transmit data line SSInDAT0/SSInTX is in a tristate condition
•
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
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. The master SSInDAT0 and SSInTX output is enabled. After an
additional one-half SSInClk period, both master and slave valid data are enabled onto their respective
transmission lines. At the same time, the SSInClk is enabled with a rising edge transition.
Data is then captured on the falling edges and propagated on the rising edges of the SSInClk signal.
In the case of a single word transfer, after all bits have been transferred, the SSInFss line is returned to its
idle High state one SSInClk period after the last bit has been captured.
For continuous back-to-back transfers, the SSInFss pin is held Low between successive data words, and
termination is the same as that of the single word transfer.
23.3.7.5 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
and
.
NOTE:
This Freescale SPI frame format configuration is only available when operating in legacy SSI
mode of operation.
NOTE: Q is undefined.
Figure 23-7. Freescale SPI Frame Format (Single Transfer) With SPO = 1 and SPH = 0
Figure 23-8. Freescale SPI Frame Format (Continuous Transfer) With SPO = 1 and SPH = 0
In this configuration, during idle periods:
•
SSInClk is forced high
•
SSInFss is forced high
•
The transmit data line SSInDAT0/SSInTX is in a tristate condition
•
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
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 and SSInRX line of the master. The master SSInDAT0 and SSInTX output pad is enabled.