
ADSP-2126x SHARC Processor Hardware Reference
3-27
Program Sequencer
Restrictions on Ending Loops
The sequencer’s loop features (which optimize performance in many ways)
limit the types of instructions that may appear at or near the end of the
loop. These restrictions include:
• Nested loops cannot use the same end-of-loop instruction address.
• Nested loops with a non-counter-based loop as the outer loop must
place the end address of the outer loop at least two addresses after
the end address of the inner loop.
• Nested loops with a non-counter-based loop as the outer loop that
use the loop abort instruction,
JUMP
(LA)
, to abort the inner loop,
may not
JUMP
(LA)
to the last instruction of the outer loop.
Table 3-8. Pipelined Execution Cycles for Loop Back (Iteration)
Cycles
1
2
3
4
Execute
E – 2
1
E – 1
E
B
Decode
E – 1
E
B
B + 1
Fetch
E
B
2
B + 1
B + 2
E is the loop end instruction, and B is the loop start instruction.
1. Termination condition tests false
2. Loop start address is the top of the PC stack
Table 3-9. Pipelined Execution Cycles for Loop Termination
Cycles
1
2
3
4
Execute
E – 2
1
E – 1
E
E + 1
Decode
E – 1
E
E + 1
E + 2
Fetch
E
E + 1
2
E + 2
E + 3
E is the loop end instruction.
1. Termination condition tests true
2. Loop aborts 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 ...