
Serial Peripheral Interface (SPI) Module
MC68HC08GP32A MC68HC08GP16A Data Sheet, Rev. 1.0
196
Freescale Semiconductor
CPOL — Clock Polarity Bit
This read/write bit determines the logic state of the SPSCK pin between transmissions. (See
Figure16-5 and
Figure 16-7.) 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
Figure16-5 and
Figure 16-7.) 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 high between bytes. (See
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
16.81 = 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
16.12.2 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
Address: $0011
Bit 7
654321
Bit 0
Read:
SPRF
ERRIE
OVRF
MODF
SPTE
MODFEN
SPR1
SPR0
Write:
Reset:
00001000
= Unimplemented
Figure 16-15. SPI Status and Control Register (SPSCR)