MC68HC908GP32_08 Datasheet, PDF (190/266 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Serial Peripheral Interface Module (SPI)
15.13 I/O Registers
Three registers control and monitor SPI operation:
• SPI control register (SPCR)
• SPI status and control register (SPSCR)
• SPI data register (SPDR)
15.13.1 SPI Control Register
The SPI control register:
• Enables SPI module interrupt requests
• Configures the SPI module as master or slave
• Selects serial clock polarity and phase
• Configures the SPSCK, MOSI, and MISO pins as open-drain outputs
• Enables the SPI module
Address: $0010
Read:
Write:
Bit 7
SPRIE
6
5
4
3
2
1
R
SPMSTR CPOL CPHA SPWOM SPE
Reset:
0
0
1
0
1
0
0
R = Reserved
Figure 15-13. SPI Control Register (SPCR)
Bit 0
SPTIE
0
SPRIE — SPI Receiver Interrupt Enable Bit
This read/write bit enables CPU interrupt requests generated by the SPRF bit. The SPRF bit is set
when a byte transfers from the shift register to the receive data register. Reset clears the SPRIE bit.
1 = SPRF CPU interrupt requests enabled
0 = SPRF CPU interrupt requests disabled
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
15-4 and Figure 15-6.) 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
15-4 and Figure 15-6.) 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 15-12.) 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.
MC68HC908GP32 Data Sheet, Rev. 10
190
Freescale Semiconductor