Cache
Freescale Semiconductor
6-9
6.4
Functional Description
shows the general flow of a caching operation using the 16-Kbyte data cache as an example.
This chapter assumes a data cache. Instruction cache operations are similar except for writing to the cache
has no support; therefore, such notions of modified cache lines and write allocation do not apply.
6–5
CM
Cache mode. Selects the cache mode and access precision. Precise and imprecise modes are described in
Section 6.4.1.2, “Cache-Inhibited Accesses
.”
00 Cacheable, write-through
01 Cacheable, copyback
10 Cache-inhibited, precise
11 Cache-inhibited, imprecise
4
Reserved, must be cleared.
3
SP
Supervisor protect.
0 Indicates supervisor and user mode access allowed
1 Indicates only supervisor access is allowed to this address space and attempted user mode accesses
generate an access error exception
2
W
Write protect. Selects the write privilege of the memory region. This field is reserved in the instruction attribute
ACRs (ACR2–3).
0 Read and write accesses permitted
1 Write accesses not permitted
1–0
Reserved, must be cleared.
Table 6-4. ACR
n
Field Descriptions (continued)
Field
Description
Summary of Contents for MCF54455
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