MC908GR8CDWE Datasheet, PDF (301/408 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Freescale Semiconductor, Inc.
Serial Peripheral Interface (SPI)
Functional Description
The following paragraphs describe the operation of the SPI module.
20.5.1 Master Mode
The SPI operates in master mode when the SPI master bit, SPMSTR, is
set.
NOTE:
Configure the SPI modules as master or slave before enabling them.
Enable the master SPI before enabling the slave SPI. Disable the slave
SPI before disabling the master SPI. See SPI Control Register.
Only a master SPI module can initiate transmissions. Software begins
the transmission from a master SPI module by writing to the transmit
data register. If the shift register is empty, the byte immediately transfers
to the shift register, setting the SPI transmitter empty bit, SPTE. The byte
begins shifting out on the MOSI pin under the control of the serial clock.
See Figure 20-3.
MASTER MCU
SHIFT REGISTER
BAUD RATE
GENERATOR
MISO
MOSI
SPSCK
SS
MISO
MOSI
SPSCK
V_DD
SS
SLAVE MCU
SHIFT REGISTER
Figure 20-3. Full-Duplex Master-Slave Connections
MC68HC908GR8 — Rev 4.0
MOTOROLA
Serial Peripheral Interface (SPI)
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Technical Data
301