LM3S301 Luminary Micro, Inc, LM3S301 Datasheet - Page 268

• Manufacturer Part Number: LM3S301
• Description: Lm3s301 Arm Microcontroller
• Manufacturer: Luminary Micro, Inc

Synchronous Serial Interface (SSI)
13.2.4.5
268
Figure 13-6. Freescale SPI Frame Format with SPO=0 and SPH=1
In this configuration, during idle periods:
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. The master SSITx output is enabled.
After a further one half SSIClk period, both master and slave valid data is enabled onto their
respective transmission lines. At the same time, the SSIClk is enabled with a rising edge
transition.
Data is then captured on the falling edges and propagated on the rising edges of the SSIClk
signal.
In the case of a single word transfer, after all bits have been transferred, the SSIFss line is
returned to its idle High state one SSIClk period after the last bit has been captured.
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.
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 13-7 and Figure 13-8.
Figure 13-7. Freescale SPI Frame Format (Single Transfer) with SPO=1 and SPH=0
SSIClk
SSIFss
SSIClk
SSIFss
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
SSIRx
SSITx
SSIRx
SSITx
Q
MSB
MSB
MSB
MSB
Preliminary
4 to 16 bits
4 to 16 bits
LSB
LSB
LSB
LSB
July 5, 2006
Q
Q