Motorola MPC823e - Page 898

Communication Processor Module
16-444 MPC823e REFERENCE MANUAL MOTOROLA
SPI
COMMUNICATION
16
PROCESSOR MODULE
REV—Reverse Data
This bit determines the receive and transmit character bit order.
0 = Reverse data. Least-significant bit of the character transmitted and received first.
1 = Normal operation. Most-significant bit of the character transmitted and received
first.
M/S—Master/Slave
This bit configures the serial peripheral interface to operate as a master or slave.
0 = The serial peripheral interface is a slave.
1 = The serial peripheral interface is a master.
EN—Enable SPI
This bit enables serial peripheral interface operation. Configure the SPIMOSI, SPIMISO,
SPICLK, and SPISEL
pins to connect to the serial peripheral interface, as described in
Section 16.14.6 The Port B Registers. When the EN bit is cleared, the serial peripheral
interface is in a reset state and consumes minimal power, which means the SPI baud rate
generator is not functioning and the input clock is disabled.
0 = The serial peripheral interface is disabled.
1 = The serial peripheral interface is enabled.
LEN—Character Length
This field specifies the number of bits in a character. These values must be between 4 and
16 bits. If you program a value less than 4 bits, erratic behavior will occur. If the value of LEN
is less than or equal to a byte, there will be LEN number of valid bits in every byte (8 bits) in
memory. On the other hand, if the value of LEN is greater than a byte, there is LEN number
of valid bits in every half-word (16 bits) in memory.
0011 = 4-bit character length.
0100 = 5-bit character length.
0101 = 6-bit character length.
0110 = 7-bit character length.
0111 = 8-bit character length.
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1111 = 16-bit character length.
Note: You must not modify other bits of the SPMODE register when the EN bit is set.