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Even though the bus slave does not control the SCK signal, in Slave mode these values
must be identical to the master device settings to ensure proper transmission. In SPI Slave
mode, only CTAR0 is used.
The module supports four different transfer formats:
• Classic SPI with CPHA=0
• Classic SPI with CPHA=1
• Modified Transfer Format with CPHA = 0
• Modified Transfer Format with CPHA = 1
A modified transfer format is supported to allow for high-speed communication with
peripherals that require longer setup times. The module can sample the incoming data
later than halfway through the cycle to give the peripheral more setup time. The MTFE
bit in the MCR selects between Classic SPI Format and Modified Transfer Format.
In the SPI configurations, the module provides the option of keeping the PCS signals
asserted between frames. See Continuous Selection Format for details.
46.4.4.1 Classic SPI Transfer Format (CPHA = 0)
The transfer format shown in following figure is used to communicate with peripheral
SPI slave devices where the first data bit is available on the first clock edge. In this
format, the master and slave sample their SIN pins on the odd-numbered SCK edges and
change the data on their SOUT pins on the even-numbered SCK edges.
Chapter 46 Serial Peripheral Interface (SPI)
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
Freescale Semiconductor, Inc.
Preliminary
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