MC9S12P128 Datasheet, PDF (403/564 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

Serial Peripheral Interface (S12SPIV5)
Table 12-4. SPICR2 Field Descriptions
Field
Description
6
XFRW
4
MODFEN
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 12.3.2.4, “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
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 12-3. 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
Serial Pin Control Bit 0 — This bit enables bidirectional pin configurations as shown in Table 12-5. In master
SPC0 mode, a change of this bit will abort a transmission in progress and force the SPI system into idle state.
1. n is used later in this document as a placeholder for the selected transfer width.
Pin Mode
Normal
Bidirectional
Normal
Bidirectional
Table 12-5. Bidirectional Pin Configurations
SPC0
0
1
0
1
BIDIROE
MISO
Master Mode of Operation
X
Master In
0
MISO not used by SPI
1
Slave Mode of Operation
X
Slave Out
0
Slave In
1
Slave I/O
MOSI
Master Out
Master In
Master I/O
Slave In
MOSI not used by SPI
S12P-Family Reference Manual, Rev. 1.12
Freescale Semiconductor
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