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Local Memory
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
4-8
Freescale Semiconductor
Figure 4-3. Instruction Cache Block Diagram
4.5.2
Instruction Cache Operation
The instruction cache is physically connected to the ColdFire core's local bus, allowing it to service all
instruction fetches from the ColdFire core and certain memory fetches initiated by the debug module.
Typically, the debug module's memory references appear as supervisor data accesses but the unit can be
programmed to generate user-mode accesses and/or instruction fetches. The instruction cache processes
any instruction fetch access in the normal manner.
4.5.2.1
Interaction with Other Modules
Because both the instruction cache and high-speed SRAM module are connected to the ColdFire core's
local data bus, certain user-defined configurations can result in simultaneous instruction fetch processing.
If the referenced address is mapped into the SRAM module, that module services the request in a single
cycle. In this case, data accessed from the instruction cache is discarded without generating external
memory references. If the address is not mapped into SRAM space, the instruction cache handles the
request in the normal fashion.
4.5.2.2
Cache Coherency and Invalidation
The instruction cache does not monitor ColdFire core data references for accesses to cached instructions.
Therefore, software must maintain cache coherency by invalidating the appropriate cache entries after
modifying code segments.
31
9
43
0
1
2
31
4
=
31
9
31
0
63
31
0
0
Local Address Bus
Line
Buffer
Address
External Data[31:0]
Line Buffer Data Storage
MUX
Data
Fill Hit
Tag
V
a
lid
Local Data Bus
Tag Hit
=
MUX