
Interrupts and Sequencing
3-50
ADSP-2126x SHARC Processor Hardware Reference
Except for reset, all interrupt service routines should end with a
return-from-interrupt (
RTI
) instruction. After reset, the PC stack is empty,
so there is no return address. The last instruction of the reset service rou-
tine should be a
JUMP
to the start of the program.
If programs force an interrupt by writing to a bit in the
IRPTL
register, the
processor recognizes the interrupt in the following cycle, and two cycles of
branching to the interrupt vector follow the recognition cycle.
The DSP responds to interrupts in three stages: synchronization and
latching (1 cycle), recognition (1 cycle), and branching to the interrupt
vector (2 cycles).
, and
show the pipe-
lined execution cycles for interrupt processing.
Table 3-21. Pipelined Execution Cycles for Interrupt During Single Cycle
Instruction
Cycles
1
2
3
4
5
Execute
N – 1
1
N
NOP
NOP
V
Decode
N
N + 1 –>
NOP
3
N + 2 –>
NOP
5
V
V + 1
Fetch
N + 1
N + 2
2
V
4
V + 1
V + 2
N is the loop start instruction and N + 3 is the instruction after the loop.
1. Interrupt occurs
2. Interrupt recognized
3. N + 1 pushed on PC stack; N + 1 suppressed
4. Interrupt Vector output
5. N + 2 suppressed
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 ...