Serial Peripheral Interface (S12SPIV5)
MC9S12XHY-Family Reference Manual Rev. 1.01
Freescale Semiconductor
499
Table 15-3. SPICR2 Field Descriptions
Field
Description
6
XFRW
Transfer Width — This bit is used for selecting the data transfer width. If 8-bit transfer width is selected, SPIDRL
becomes the dedicated data register and SPIDRH is unused. If 16-bit transfer width is selected, SPIDRH and
SPIDRL form a 16-bit data register. Please refer to
Section 15.3.2.4, “SPI Status Register (SPISR)
for
information about transmit/receive data handling and the interrupt flag clearing mechanism. In master mode, a
change of this bit will abort a transmission in progress and force the SPI system into idle state.
0 8-bit Transfer Width (n = 8)
1
1 16-bit Transfer Width (n = 16)
1
1
n is used later in this document as a placeholder for the selected transfer width.
4
MODFEN
Mode Fault Enable Bit — This bit allows the MODF failure to be detected. If the SPI is in master mode and
MODFEN is cleared, then the SS port pin is not used by the SPI. In slave mode, the SS is available only as an
input regardless of the value of MODFEN. For an overview on the impact of the MODFEN bit on the SS port pin
configuration, refer to
Table 15-2
. In master mode, a change of this bit will abort a transmission in progress and
force the SPI system into idle state.
0 SS port pin is not used by the SPI.
1 SS port pin with MODF feature.
3
BIDIROE
Output Enable in the Bidirectional Mode of Operation — This bit controls the MOSI and MISO output buffer
of the SPI, when in bidirectional mode of operation (SPC0 is set). In master mode, this bit controls the output
buffer of the MOSI port, in slave mode it controls the output buffer of the MISO port. In master mode, with SPC0
set, a change of this bit will abort a transmission in progress and force the SPI into idle state.
0 Output buffer disabled.
1 Output buffer enabled.
1
SPISWAI
SPI Stop in Wait Mode Bit — This bit is used for power conservation while in wait mode.
0 SPI clock operates normally in wait mode.
1 Stop SPI clock generation when in wait mode.
0
SPC0
Serial Pin Control Bit 0 — This bit enables bidirectional pin configurations as shown in
Table 15-4
. In master
mode, a change of this bit will abort a transmission in progress and force the SPI system into idle state.
Table 15-4. Bidirectional Pin Configurations
Pin Mode
SPC0
BIDIROE
MISO
MOSI
Master Mode of Operation
Normal
0
X
Master In
Master Out
Bidirectional
1
0
MISO not used by SPI
Master In
1
Master I/O
Slave Mode of Operation
Normal
0
X
Slave Out
Slave In
Bidirectional
1
0
Slave In
MOSI not used by SPI
1
Slave I/O
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