
I/O Registers
MC68HC08AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
231
When CPHA = 1 for a slave, the first edge of the SPSCK indicates the beginning of the transmission.
The same applies when SS is high for a slave. The MISO pin is held in a high-impedance state, and
the incoming SPSCK is ignored. In certain cases, it may also cause the MODF flag to be set. See
way.
SPWOM — SPI Wired-OR Mode
This read/write bit disables the pull-up 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 (SPSCR)
The SPI status and control register contains flags to signal the following 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 the following functions:
Enable error interrupts
Enable mode fault error detection
Select master SPI baud rate
SPRF — SPI Receiver Full
This clearable, read-only flag is set each time a byte transfers from the shift register to the receive data
register. SPRF generates a CPU interrupt request if the SPRIE bit in the SPI control register is set also.
Address: $0011
Bit 7
654321
Bit 0
Read:
SPRF
ERRIE
OVRF
MODF
SPTE
MODFEN
SPR1
SPR0
Write:
Reset:
00001000
= Unimplemented
Figure 16-14. SPI Status and Control Register (SPSCR)