MC68HC08AS32 Datasheet, PDF (293/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Serial Peripheral Interface (SPI)
Queuing Transmission Data
SPTE SPTIE SPE
SPRIE SPRF
SPI TRANSMITTER
CPU INTERRUPT REQUEST
ERRIE
MODF
OVRF
SPI RECEIVER/ERROR
CPU INTERRUPT REQUEST
Figure 18-9. SPI Interrupt Request Generation
Two sources in the SPI status and control register can generate CPU
interrupt requests:
1. SPI receiver full bit (SPRF) — The SPRF bit 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 can generate an SPI receiver/error CPU interrupt request.
2. SPI transmitter empty (SPTE) — The SPTE bit 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 can generate an SPTE CPU interrupt request.
18.9 Queuing Transmission Data
The double-buffered transmit data register allows a data byte to be
queued and transmitted. For an SPI configured as a master, a queued
data byte is transmitted immediately after the previous transmission has
completed. The SPI transmitter empty flag (SPTE in SPSCR) indicates
when the transmit data buffer is ready to accept new data. Write to the
SPI data register only when the SPTE bit is high. Figure 18-10 shows
the timing associated with doing back-to-back transmissions with the
SPI (SPSCK has CPHA–CPOL = 1–0).
MC68HC08AS32 — Rev. 3.0
MOTOROLA
Serial Peripheral Interface (SPI)
Advance Information
293