Freescale Semiconductor HCS08 Series, Reference Manual

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16-Bit Serial Peripheral Interface (S08SPI16V1)
MC9S08JS16 MCU Series Reference Manual, Rev. 4
206 Freescale Semiconductor
NOTE
Care must be taken when using the SS output feature in a multi-master
system since the mode fault feature is not available for detecting system
errors between masters.
13.4.7.2 Bidirectional Mode (MOMI or SISO)
The bidirectional mode is selected when the SPC0 bit is set in SPI Control Register 2 (see
Section Table 13-9., “Normal Mode and Bidirectional Mode .”) In this mode, the SPI uses only one serial
data pin for the interface with external device(s). The MSTR bit decides which pin to use. The MOSI pin
becomes the 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 MISO pin in master mode and MOSI pin in slave mode are not used
by the SPI.
The direction of each serial I/O pin depends on the BIDIROE bit. If the pin is configured as an output,
serial data from the shift register is driven out on the pin. The same pin is also the serial input to the shift
register.
The SPSCK is output for the master mode and input for the slave mode.
The SS is the input or output for the master mode, and it is always the input for the slave mode.
The bidirectional mode does not affect SPSCK and SS functions.
Table 13-9. Normal Mode and Bidirectional Mode
When SPE = 1 Master Mode MSTR = 1 Slave Mode MSTR = 0
Normal Mode
SPC0 = 0
Bidirectional Mode
SPC0 = 1
SPI
MOSI
MISO
Serial Out
Serial In
SPI
MOSI
MISO
Serial In
Serial Out
SPI
MOMI
Serial Out
Serial In
BIDIROE
SPI
SISO
Serial In
Serial Out
.
BIDIROE