Serial Peripheral Interface (SPI)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
30-6
Freescale Semiconductor
30.4
SPI Registers
The following sections describe the registers used in configuring and operating the SPI.
30.4.1
SPI Mode Register (SPMODE)
The SPI mode register (SPMODE), shown in
Figure 30-4
, controls both the SPI operation mode and clock
source.
This register is affected by HRESET and SRESET.
Table 30-1
describes the SPMODE fields.
0
1
2
3
4
5
6
7
8
11
12
15
Field
—
LOOP
CI
CP
DIV16
REV
M/S
EN
LEN
PM
Reset
0000_00
—
0_0000_0000
R/W
R/W
Addr
0xAA0
Figure 30-4. SPI Mode Register (SPMODE)
Table 30-1. SPMODE Field Descriptions
Bits
Name
Description
0
—
Reserved, should be cleared.
1
LOOP
Loop mode. Enables local loopback operation.
0 Normal operation
1 Loopback mode. The transmitter output is internally connected to the receiver input. The receiver
and transmitter operate normally, except that received data is ignored.
2
CI
Clock invert. Inverts SPI clock polarity. See
Figure 30-5
and
Figure 30-6
.
0 The inactive state of SPICLK is low.
1 The inactive state of SPICLK is high.
3
CP
Clock phase. Selects the transfer format. See
Figure 30-5
and
Figure 30-6
.
0 SPICLK starts toggling at the middle of the data transfer.
1 SPICLK starts toggling at the beginning of the data transfer.
4
DIV16
Divide by 16. Selects the clock source for the SPI baud rate generator when configured as an SPI
master. In slave mode, SPICLK is the clock source.
0 BRGCLK is the input to the SPI BRG.
1 BRGCLK/16 is the input to the SPI BRG.
5
REV
Reverse data. Determines the receive and transmit character bit order.
0 Reverse data—lsb of the character sent and received first.
1 Normal operation—msb of the character sent and received first.
6
M/S
Master/slave. Selects master or slave mode.
0 The SPI is a slave.
1 The SPI is a master.
Note:
Master/slave mode is undefined at reset.
7
EN
Enable SPI. Do not change other SPMODE bits when EN is set.
0 The SPI is disabled. The SPI is in a reset state and consumes minimal power. The SPI BRG is
not functioning and the input clock is disabled.
1 The SPI is enabled.
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