Datasheet

I/O Registers
MC68HC908GR60A • MC68HC908GR48A • MC68HC908GR32A Data Sheet, Rev. 5
Freescale Semiconductor 219
SPRF — SPI Receiver Full Bit
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.
During an SPRF CPU interrupt, the CPU clears SPRF by reading the SPI status and control register
with SPRF set and then reading the SPI data register.
Reset clears the SPRF bit.
1 = Receive data register full
0 = Receive data register not full
ERRIE — Error Interrupt Enable Bit
This read/write bit enables the MODF and OVRF bits to generate CPU interrupt requests. Reset clears
the ERRIE bit.
1 = MODF and OVRF can generate CPU interrupt requests
0 = MODF and OVRF cannot generate CPU interrupt requests
OVRF — Overflow Bit
This clearable, read-only flag is set if software does not read the byte in the receive data register before
the next full byte enters the shift register. In an overflow condition, the byte already in the receive data
register is unaffected, and the byte that shifted in last is lost. Clear the OVRF bit by reading the SPI
status and control register with OVRF set and then reading the receive data register. Reset clears the
OVRF bit.
1 = Overflow
0 = No overflow
MODF — Mode Fault Bit
This clearable, read-only flag is set in a slave SPI if the SS
pin goes high during a transmission with
MODFEN set. In a master SPI, the MODF flag is set if the SS
pin goes low at any time with the
MODFEN bit set. Clear MODF by reading the SPI status and control register (SPSCR) with MODF set
and then writing to the SPI control register (SPCR). Reset clears the MODF bit.
1 = SS
pin at inappropriate logic level
0 = SS
pin at appropriate logic level
SPTE — SPI Transmitter Empty Bit
This clearable, read-only flag is set each time the transmit data register transfers a byte into the shift
register. SPTE generates an SPTE CPU interrupt request if SPTIE in the SPI control register is set
also.
NOTE
Do not write to the SPI data register unless SPTE is high.
During an SPTE CPU interrupt, the CPU clears SPTE by writing to the transmit data register.
Reset sets the SPTE bit.
1 = Transmit data register empty
0 = Transmit data register not empty
MODFEN — Mode Fault Enable Bit
This read/write bit, when set, allows the MODF flag to be set. If the MODF flag is set, clearing MODFEN
does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is 0, then the SS
pin is available as a general-purpose I/O.
If the MODFEN bit is 1, then the SS
pin is not available as a general-purpose I/O. When the SPI is
enabled as a slave, the SS
pin is not available as a general-purpose I/O regardless of the value of
MODFEN. See 15.11.4 SS (Slave Select).