Motorola MC68HC908AB32 - Page 305

Serial Peripheral Interface Module (SPI)
I/O Registers
MC68HC908AB32 — Rev. 1.0 Technical Data
MOTOROLA Serial Peripheral Interface Module (SPI) 305
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 16-4 and Figure 16-6.) 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 16-4 and Figure 16-6.) 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 16-12.) 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 16.10 Resetting the SPI.) Reset clears
the SPE bit.
1 = SPI module enabled
0 = SPI module disabled
SPTIE— SPI Transmit Interrupt Enable
This read/write bit enables CPU interrupt requests generated by the
SPTE bit. SPTE is set when a byte transfers from the transmit data
register to the shift register. Reset clears the SPTIE bit.
1 = SPTE CPU interrupt requests enabled
0 = SPTE CPU interrupt requests disabled