
Local Memory
MCF5272 ColdFire Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
4-13
Table 4-8. CACR Field Descriptions
Bits
Name
Description
31
CENB
Enable cache.
0 Cache disabled. The cache is not operational, but data and tags are preserved.
1 Cache enabled.
30–29
—
Reserved, should be cleared.
28
CDPI
Disable CPUSHL invalidation.
0 Cache disabled
1 Cache enabled
27
CFRZ
Cache freeze. Allows the user to freeze the contents of the cache. When CFRZ is asserted line fetches
can be initiated and loaded into the line-fill buffer, but a valid cache entry can not be overwritten. If a given
cache location is invalid, the contents of the line-fill buffer can be written into the memory array while CFRZ
is asserted.
0 Normal operation
1 Freeze valid cache lines
26–25
—
Reserved, should be cleared.
24
CINVA
Cache invalidate all. Writing a 1 to this bit initiates entire cache invalidation. Note the caches are not
cleared on power-up or normal reset.
0 No invalidation is performed.
1 Initiate invalidation of the entire cache. The cache controller sequentially clears V in all sets.
Subsequent accesses stall until invalidation finishes, at which point, CINVA is automatically cleared.
This operation takes 64 clock cycles.
23–11
—
Reserved, should be cleared.
10
CEIB
Default noncacheable fill buffer. Determines if the fill buffer can store noncacheable accesses
0 Fill buffer not used to store noncacheable instruction accesses (16 or 32 bits).
1 Fill buffer used to store noncacheable accesses. The fill buffer is used only for normal (TT = 0)
instruction reads of a noncacheable region. Instructions are loaded into the fill buffer by a burst access
(same as a line fill). They stay in the buffer until they are displaced, so subsequent accesses may not
appear on the external bus.
Note that this feature can cause a coherency problem for self-modifying code. If CEIB = 1 and a
cache-inhibited access uses the fill buffer, instructions remain valid in the fill buffer until a
cache-invalidate-all instruction, another cache-inhibited burst, or a miss that initiates a fill.
9
DCM
0 Default cacheable
1 Default noncacheable
8
DBWE
Default buffered write enable. Defines the default value for enabling buffered writes. Generally, enabled
buffered writes provide higher system performance but recovery from access errors can be more difficult.
For the ColdFire CPU, reporting access errors on operand writes is always imprecise and enabling
buffered writes simply 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
completes.
1 A local bus write cycle is terminated immediately and the operation buffered in the bus controller.
Operand write cycles are effectively decoupled between the processor's local bus and the external bus.
7–6
—
Reserved, should be cleared.
5
DWP
Default write protect.
0 Read and write accesses permitted
1 Write accesses not permitted
4–2
—
Reserved, should be cleared.