ADSP-2126x SHARC Processor Hardware Reference
3-29
Program Sequencer
iterate only once or twice and loops of length two that iterate only once
incur two cycles of overhead, because two aborted instructions after the
last iteration are needed to clear the instruction pipeline.
Table 3-10. Pipelined Execution Cycles for Single Instruction
Counter-based Loop with Three Iterations
Cycles
1
2
3
4
5
Execute
N
1
N + 1 (Pass 1) N + 1 (Pass 2) N + 1 (Pass 3) N + 2
Decode
N + 1
N + 1
N + 1
N + 2
N + 3
Fetch
N + 2
N + 1
2
N + 2
3
N + 3
N + 4
N is the loop start instruction and N + 2 is the instruction after the loop.
1. Loop count (LCNTR) equals 3
2. No opcode latch or fetch address update; count expired tests true
3. Loop iteration aborts; PC and loop stacks pop
Table 3-11. Pipelined Execution Cycles for Single Instruction
Counter-based Loop with Two Iterations (Two Overhead Cycles)
Cycles
1
2
3
4
5
6
Execute
N
1
N + 1 (Pass 1) N + 1 (Pass 2) NOP
NOP
N + 2
Decode
N + 1
N + 1
N + 1 –>
NOP
4
N + 1 –>
NOP
5
N + 2
N + 3
Fetch
N + 2
N + 1
2
N + 1
3
N + 2
N + 3
N + 4
N is the loop start instruction and N + 3 is the instruction after the loop.
1. Loop count (LCNTR) equals 2
2. PC Stack supplies loop start address
3. Count expired tests true
4. Loop iteration aborts; PC and loop stacks pop
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 ...