Instruction Cache
3-8
ADSP-2126x SHARC Processor Hardware Reference
are made to the same block in internal memory. This scenario occurs
when data is accessed from the same block from which the instructions are
executed. This scenario also occurs when an instruction performs both a
DM and PM access to the same block in one instruction. In the first case,
the instruction takes two cycles to complete, with the data being accessed
in the first cycle and the instruction in the second. In the latter case, where
a dual data access is performed, the processor takes three cycles to com-
plete the instruction.
Block conflicts are not cached.
Using the Cache
After a DSP reset, the cache is cleared (it contains no instructions), unfro-
zen, and enabled. From then on, the
MODE2
register controls the operating
mode of the instruction cache as shown below.
•
Cache Disable.
Bit 4 (
CADIS
) directs the sequencer to disable the
cache (if 1) or enable the cache (if 0).
•
Cache Freeze.
Bit 19 (
CAFRZ
) directs the sequencer to freeze the
contents of the cache (if 1) or let new entries displace the entries in
the cache (if 0).
MODE2
register.
Freezing the cache prevents any changes to its contents—a cache miss does
not result in a new instruction being stored in the cache. Disabling the
cache stops its operation completely; all instruction fetches conflicting
with program memory data accesses are delayed by the access. These func-
tions are selected by the
CADIS
(cache enable/disable) and
CAFRZ
(cache
freeze) bits in the
MODE2
register.
The cache content stays valid when the cache is disabled. The effect of dis-
abling the cache is that an already cached instruction does not generate a
Summary of Contents for ADSP-21261 SHARC
Page 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Page 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Page 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Page 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Page 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Page 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Page 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Page 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Page 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Page 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Page 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Page 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Page 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...