ADSP-2126x SHARC Processor Hardware Reference
3-31
Program Sequencer
Similarly, in a one instruction loop that iterates at least three times, pro-
cessing is delayed by one cycle if the interrupt occurs during the
third-to-last iteration. For more information on pipeline execution during
interrupts, see
“Interrupts and Sequencing” on page 3-48
.
Short noncounter-based loops terminate differently from short
counter-based loops. These differences stem from the architecture of the
pipeline and conditional logic:
• In a three instruction non counter-based loop, the sequencer tests
the termination condition when the DSP executes the top of loop
instruction. When the condition tests true, the sequencer com-
pletes the iteration of the loop and terminates.
• In a two instruction non counter-based loop, the sequencer tests
the termination condition when the DSP executes the last (second)
instruction. If the condition becomes true when the first instruc-
tion is executed, and the condition tests true during the second
instruction, then the sequencer completes one more iteration of the
loop before exiting. If the condition becomes true during the sec-
ond instruction, the sequencer completes two more iterations of
the loop before exiting.
• In a one instruction non counter-based loop, the sequencer tests
the termination condition every cycle. After the cycle when the
condition becomes true, the sequencer completes three more itera-
tions of the loop before exiting. But if the one instruction used in
the loop is a PM instruction, then the loop is executed only two
more times.
Loop Address Stack
The sequencer’s loop support, shown in
, includes
a loop address stack. The loop address stack is six levels deep by 32 bits
wide.
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 ...