MC9S08JM16 Datasheet, PDF (259/386 Pages) Freescale Semiconductor, Inc – Microcontrollers

When SPE = 1
Serial Peripheral Interface (S08SPI16V1)
Table 15-9. Normal Mode and Bidirectional Mode
Master Mode MSTR = 1
Slave Mode MSTR = 0
Normal Mode
SPC0 = 0
Serial Out
SPI
Serial In
MOSI
MISO
Serial In
SPI
Serial Out
MOSI
MISO
Bidirectional Mode
SPC0 = 1
Serial Out
SPI
Serial In
BIDIROE
MOMI
Serial In
SPI
Serial Out
BIDIROE
SISO
.
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.
NOTE
In bidirectional master mode, with mode fault enabled, both data pins MISO
and MOSI can be occupied by the SPI, though MOSI is normally used for
transmissions in bidirectional mode and MISO is not used by the SPI. If a
mode fault occurs, the SPI is automatically switched to slave mode, in this
case MISO becomes occupied by the SPI and MOSI is not used. This has to
be considered, if the MISO pin is used for another purpose.
15.4.8 Error Conditions
The SPI has one error condition:
• Mode fault error
15.4.8.1 Mode Fault Error
If the SS input becomes low while the SPI is configured as a master, it indicates a system error where more
than one master may be trying to drive the MOSI and SPSCK lines simultaneously. This condition is not
permitted in normal operation, and the MODF bit in the SPI status register is set automatically provided
the MODFEN bit is set.
MC9S08JM16 Series Data Sheet, Rev. 2
Freescale Semiconductor
259