MC68HC908GZ8 Datasheet, PDF (294/344 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Serial Peripheral Interface (SPI) Module
CPOL — Clock Polarity Bit
This read/write bit determines the logic state of the SPSCK pin between
transmissions. (See Figure 21-4 and Figure 21-6.) 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 21-4 and Figure 21-6.) 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 21-12.) 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 21.9 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
21.13.2 SPI Status and Control Register
The SPI status and control register contains flags to signal these conditions:
• Receive data register full
• Failure to clear SPRF bit before next byte is received (overflow error)
• Inconsistent logic level on SS pin (mode fault error)
• Transmit data register empty
The SPI status and control register also contains bits that perform these functions:
• Enable error interrupts
• Enable mode fault error detection
• Select master SPI baud rate
Data Sheet
294
Serial Peripheral Interface (SPI) Module
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MC68HC908GZ8
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