MC68HC908GR8A_07 Datasheet, PDF (187/260 Pages) Freescale Semiconductor, Inc – Microcontrollers

Flag
SPTE
Transmitter empty
SPRF
Receiver full
OVRF
Overflow
MODF
Mode fault
Table 15-1. SPI Interrupts
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 SPRF to generate receiver CPU interrupt requests,
regardless of the state of SPE. See Figure 15-12.
The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error
CPU interrupt request.
SPTE SPTIE _SPE
SPI TRANSMITTER
CPU INTERRUPT REQUEST
SPRIE SPRF
ERRIE
MODF
OVRF
SPI RECEIVER/ERROR
CPU INTERRUPT REQUEST
Figure 15-12. SPI Interrupt Request Generation
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.
• The following sources in the SPI status and control register can generate CPU interrupt requests:
• SPI receiver full bit (SPRF) — SPRF becomes set every time a byte transfers from the shift register
to the receive data register. If the SPI receiver interrupt enable bit, SPRIE, is also set, SPRF
generates an SPI receiver/error CPU interrupt request.
• SPI transmitter empty (SPTE) — SPTE becomes set every time a byte transfers from the transmit
data register to the shift register. If the SPI transmit interrupt enable bit, SPTIE, is also set, SPTE
generates an SPTE CPU interrupt request.
MC68HC908GR8A • MC68HC908GR4A Data Sheet, Rev. 5
Freescale Semiconductor
187