MC68HC908GR8 Datasheet, PDF (217/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

20.8 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt requests.
Table 20-2. SPI Interrupts
Flag
SPTE
Transmitter empty
SPRF
Receiver full
OVRF
Overflow
MODF
Mode fault
Request
SPI transmitter CPU interrupt request
(SPTIE = 1, SPE = 1)
SPI receiver CPU interrupt request
(SPRIE = 1)
SPI receiver/error interrupt request (ERRIE = 1)
SPI receiver/error interrupt request (ERRIE = 1)
Interrupts
Reading the SPI status and control register with SPRF set and then reading the receive data register
clears SPRF. The clearing mechanism for the SPTE flag is always just a write to the transmit data register.
The SPI transmitter interrupt enable bit (SPTIE) enables the SPTE flag to generate transmitter CPU
interrupt requests, provided that the SPI is enabled (SPE = 1).
The SPI receiver interrupt enable bit (SPRIE) enables the SPRF bit to generate receiver CPU interrupt
requests, regardless of the state of the SPE bit. See Figure 20-11.
The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error
CPU interrupt request.
The mode fault enable bit (MODFEN) can prevent the MODF flag from being set so that only the OVRF
bit is enabled by the ERRIE bit to generate receiver/error CPU interrupt requests.
SPTE SPTIE SPE
SPRIE SPRF
SPI TRANSMITTER
CPU INTERRUPT REQUEST
ERRIE
MODF
OVRF
SPI RECEIVER/ERROR
CPU INTERRUPT REQUEST
Figure 20-11. SPI Interrupt Request Generation
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
Freescale Semiconductor
217