Motorola MPC860 PowerQUICC, User Manual

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MOTOROLA Chapter 31. Serial Peripheral Interface 31-9
Part V. The Communications Processor Module
31.4.1.2 SPI Examples with Different SPMODE[LEN] Values
The examples below show how SPMODE[LEN] is used to determine character length. To
help map the process, the conventions shown in Table 31-2 are used in the examples.
For all examples below, assume the memory contains the following binary image:
msb ghij_klmn__opqr_stuv lsb
Example 1
with LEN=4 (data size=5), the following data is selected:
msb xxxj_klmn__xxxr_stuv lsb
with REV=0, the order of the string appearing on the line is:
first nmlk_j__vuts_r last
with REV=1, the order of the string appearing on the line is:
first j_klmn__r_stuv last
Example 2
with LEN=7 (data size=8), the following data is selected:
msb ghij_klmn__opqr_stuv lsb
with REV=0, the string transmitted is:
first nmlk_jihg__vuts_rqpo last
with REV=1, the string is transmitted:
first ghij_klmn__opqr_stuv last
Example 3
with LEN=0xC (data size=13), the following data is selected:
msb ghij_klmn__xxxr_stuv lsb
with REV=0, the string transmitted:
first nmlk_jihg__vuts_r last
with REV=1, the string is transmitted:
first ghij_klmn__r_stuv last
1
Both __ and _ are used to aid readability.
Table 31-2. Example Conventions
Convention Description
g
Ð
v
Binary symbols
x
Deleted bit
__
1
Original byte boundary
_
1
Original 4-bit boundary.