4-16
MCF5272 User’s Manual
Instruction Cache Overview
14–13
SM
Supervisor mode. Specifies whether only user or supervisor accesses are allowed in this address
range or if the type of access is a don’t care.
00 Match addresses only in user mode
01 Match addresses only in supervisor mode
1x Execute cache matching on all accesses
12–7
—
Reserved; should be cleared.
6
CM
Cache mode. Defines whether the memory access is cacheable or noncacheable.
0 Caching enabled
1 Caching disabled
5
BWE
Buffered write enable. Generally, the enabling of buffered writes provides higher system
performance but recovery from access errors may be more difficult. For the ColdFire CPU, reporting
access errors on operand writes is always imprecise; enabling buffered writes further decouples the
write instruction from the signaling of the fault.
0 Termination of an operand write cycle on the processor's local bus is delayed until the external
bus cycle is completed.
1 A write cycle on the local bus is terminated immediately and the operation is then buffered in the
bus controller. In this mode, operand write cycles are effectively decoupled between the
processor's local bus and the external bus.
4–3
—
Reserved, should be cleared.
2
WP
Write protect. Selects the write privilege of the memory region.
0 Read and write accesses permitted
1 Write accesses not permitted
1–0
—
Reserved, should be cleared.
Table 4-9. ACRn Field Descriptions (Continued)
Bits
Name
Description
Содержание DigitalDNA ColdFire MCF5272
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