Serial Peripheral Interface Module (SPI)
I/O Registers
MC68HC908GP32
•
MC68HC08GP32
—
Rev. 6
Technical Data
MOTOROLA
Serial Peripheral Interface Module (SPI)
329
DMAS — DMA Select Bit
This read only bit has no effect on this version of the SPI. This bit
always reads as a 0.
0 = SPRF DMA and SPTE DMA service requests disabled
(SPRF CPU and SPTE CPU interrupt requests enabled)
SPMSTR — SPI Master Bit
This read/write bit selects master mode operation or slave mode
operation. Reset sets the SPMSTR bit.
1 = Master mode
0 = Slave mode
CPOL — Clock Polarity Bit
This read/write bit determines the logic state of the SPSCK pin
between transmissions. (See
Figure 20-4
and
Figure 20-6
.) To
transmit data between SPI modules, the SPI modules must have
identical CPOL values. Reset clears the CPOL bit.
CPHA — Clock Phase Bit
This read/write bit controls the timing relationship between the serial
clock and SPI data. (See
Figure 20-4
and
Figure 20-6
.) To transmit
data between SPI modules, the SPI modules must have identical
CPHA values. When CPHA = 0, the SS pin of the slave SPI module
must be set to logic 1 between bytes.
(See
Figure 20-12
.) Reset sets
the CPHA bit.
SPWOM — SPI Wired-OR Mode Bit
This read/write bit disables the pullup devices on pins SPSCK, MOSI,
and MISO so that those pins become open-drain outputs.
1 = Wired-OR SPSCK, MOSI, and MISO pins
0 = Normal push-pull SPSCK, MOSI, and MISO pins
SPE — SPI Enable
This read/write bit enables the SPI module. Clearing SPE causes a
partial reset of the SPI.
(See
20.10 Resetting the SPI
.) Reset clears
the SPE bit.
1 = SPI module enabled
0 = SPI module disabled
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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