mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 465

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

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.
20.4.9
The SPI has one error condition:
20.4.9.1
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
Freescale Semiconductor
•
Bidirectional Mode
When SPE = 1
Normal Mode
Mode fault error
SPC0 = 0
SPC0 = 1
Error Conditions
Mode Fault Error
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.
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
Serial Out
Serial In
Serial Out
SPI
Table 20-11. Normal Mode and Bidirectional Mode
Serial In
SPI
Master Mode MSTR = 1
BIDIROE
NOTE
MOMI
MOSI
MISO
.
Serial Out
Serial In
Serial Out
SPI
Serial In
SPI
Slave Mode MSTR = 0
16-Bit Serial Peripheral Interface (SPI16)
BIDIROE
SISO
MOSI
MISO
20-25