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MCF51QE128 MCU Series Reference Manual, Rev. 3
322 Freescale Semiconductor
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NOTE
Ensure that the SPI should not be disabled (SPE = 0) at the same time as a
bit change to SPIxC1[CPHA]. These changes should be performed as
separate operations or unexpected behavior may occur.
16.4.2 SPI Control Register 2 (SPIxC2)
This read/write register controls optional features of the SPI system. Bits 7, 6, 5, and 2 are reserved and
always read 0.
5
SPTIE
SPI Transmit Interrupt Enable. This is the interrupt enable bit for SPI transmit buffer empty (SPTEF).
0 Interrupts from SPTEF inhibited (use polling)
1 When SPTEF is 1, hardware interrupt requested
4
MSTR
Master/Slave Mode Select
0 SPI module configured as a slave SPI device
1 SPI module configured as a master SPI device
3
CPOL
Clock Polarity. This bit effectively places an inverter in series with the clock signal from a master SPI or to a slave
SPI device. Refer to Section 16.5.1, “SPI Clock Formats” for more details.
0 Active-high SPI clock (idles low)
1 Active-low SPI clock (idles high)
2
CPHA
Clock Phase. This bit selects one of two clock formats for different synchronous serial peripheral devices. Refer
to Section 16.5.1, “SPI Clock Formats” for more details.
0 First edge on SPSCK occurs at the middle of the first cycle of an 8-cycle data transfer
1 First edge on SPSCK occurs at the start of the first cycle of an 8-cycle data transfer
1
SSOE
Slave Select Output Enable. This bit is used with the mode fault enable (SPIxC2[MODFEN]) bit and the
master/slave (MSTR) control bit to determine the function of the SS pin as shown in Table 16-2.
0
LSBFE
lsb First (Shifter Direction)
0 SPI serial data transfers start with most significant bit
1 SPI serial data transfers start with least significant bit
Table 16-2. SS Pin Function
MODFEN SSOE Master Mode Slave Mode
0 0 General-purpose I/O (not SPI) Slave select input
0 1 General-purpose I/O (not SPI) Slave select input
10SS
input for mode fault Slave select input
1 1 Automatic SS output Slave select input
Table 16-1. SPIxC1 Field Descriptions (continued)
Field Description