Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 838

Serial Peripheral Interface (SPI)
30.4.1.2 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
1
Both __ and _ are used to aid readability.
For all examples below, assume the memory contains the following binary image:
msb ghij_klmn__opqr_stuv
Example 1
with LEN=4 (data size=5), the following data is selected:
msb xxxj_klmn__xxxr_stuv
with REV=0, the order of the string appearing on the line is:
firstnmlk_j__vuts_r
with REV=1, the order of the string appearing on the line is:
firstj_klmn__r_stuv
Example 2
with LEN=7 (data size=8), the following data is selected:
msb ghij_klmn__opqr_stuv
with REV=0, the string transmitted is:
firstnmlk_jihg__vuts_rqpo
with REV=1, the string is transmitted:
firstghij_klmn__opqr_stuv
Example 3
with LEN=0xC (data size=13), the following data is selected:
msb ghij_klmn__xxxr_stuv
with REV=0, the string transmitted:
firstnmlk_jihg__vuts_r
with REV=1, the string is transmitted:
firstghij_klmn__r_stuv
30.4.2 SPI Event/Mask Registers (SPIE/SPIM)
The SPI event register (SPIE) generates interrupts and reports events recognized by the SPI. When an
event is recognized, the SPI sets the corresponding SPIE bit. Clear SPIE bits by writing a 1—writing 0 has
no effect. Setting a bit in the SPI mask register (SPIM) enables and clearing a bit masks the corresponding
interrupt. Unmasked SPIE bits must be cleared before the CPM clears internal interrupt requests.
Figure 30-7 shows both registers.
30-8
Table 30-2 are used in the examples.
Table 30-2. Example Conventions
Convention
g v
–
x
1
__
1
_
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Description
Binary symbols
Deleted bit
Original byte boundary
Original 4-bit boundary.
lsb
lsb
last
last
lsb
last
last
lsb
last
last
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