MC68HC908JW32_09 Datasheet, PDF (142/232 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Serial Peripheral Interface Module (SPI)
10.12.5 CGND (Clock Ground)
CGND is the ground return for the serial clock pin, SPSCK, and the ground for the port output buffers. It
is internally connected to V_SS as shown in Table 10-1.
10.13 I/O Registers
Three registers control and monitor SPI operation:
• SPI control register (SPCR)
• SPI status and control register (SPSCR)
• SPI data register (SPDR)
10.13.1 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: $004C
Bit 7
6
5
4
3
2
1
Read:
SPRIE
Write:
R
SPMSTR CPOL CPHA SPWOM SPE
Reset: 0
0
1
0
1
0
0
R
= Reserved
Figure 10-13. 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 10-4 and Figure 10-6.) 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 10-4 and Figure 10-6.) 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 10-12.) Reset sets the CPHA bit.
MC68HC908JW32 Data Sheet, Rev. 6
142
Freescale Semiconductor