MC68HC912DG128 Datasheet, PDF (266/452 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Multiple Serial Interface
14.5.4 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
Normal
Mode
SPC0=0
Serial Out
MO
SPI
DDRS5
Serial In
MI
Serial Out
MO
SPI
DDS5
Serial In
MI
SWOM enables open drain output.
Serial In
SI
SPI
DDRS4
Serial Out
SO
Serial In
SI
SPI
DDS4
Serial Out
SO
SWOM enables open drain output.
Bidirectional
Mode
SPC0=1
Serial Out
SPI
Serial In
DDRS5
MOMI
PS4
Serial In
SPI
Serial Out
DDRS4
PS5
SISO
Serial Out
SPI
Serial In
DDS5
MOMI
PS4
SWOM enables open drain output. PS4 becomes GPIO.
Serial In
SPI
Serial Out
DDS4
PS5
SISO
SWOM enables open drain output. PS5 becomes GPIO.
Figure 14-6. Normal Mode and Bidirectional Mode
Technical Data
266
MC68HC912DG128 — Rev 3.0
Multiple Serial Interface
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