Freescale Semiconductor, Inc.
Multiple Serial Interface
15.5.4 Bidirectional Mode (MOMI or SISO)
In bidirectional mode, the SPI uses only one serial data pin for external
device interface. The MSTR bit decides which pin to be used. The MOSI
pin becomes serial data I/O (MOMI) pin for the master mode, and the
MISO pin becomes serial data I/O (SISO) pin for the slave mode. The
direction of each serial I/O pin depends on the corresponding DDRS bit.
When SPE=1
Master Mode
MSTR=1
Slave Mode
MSTR=0
Serial Out
Serial In
MO
MI
SI
Normal
Mode
SPC0=0
DDS4
SPI
SPI
DDS5
Serial In
Serial Out
SO
SWOM enables open drain output.
SWOM enables open drain output.
Serial Out
Serial In
MOMI
PS4
PS5
Bidirectional
Mode
DDS4
SPI
SPI
DDS5
SPC0=1
Serial In
Serial Out
SISO
SWOM enables open drain output. PS4 becomes GPIO.
SWOM enables open drain output. PS5 becomes GPIO.
Figure 15-6. Normal Mode and Bidirectional Mode
Advance Information
254
68HC(9)12D60 — Rev 4.0
MOTOROLA
Multiple Serial Interface
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MOTOROLA [ MOTOROLA ]
