Interrupts and Sequencing
3-48
ADSP-2126x SHARC Processor Hardware Reference
loading
TCOUNT
from
TPERIOD
and the timer’s decrementing of
TCOUNT
.
Also note that
TCOUNT
and
TPERIOD
are not initialized at reset. Programs
should initialize these registers before enabling the timer.
Interrupts and Sequencing
Another type of nonsequential program flow that the sequencer supports
is interrupt processing. Interrupts may stem from a variety of conditions,
both internal and external to the processor. In response to an interrupt,
the sequencer processes a subroutine call to a predefined address, called
the interrupt vector. The DSP assigns a unique vector to each type of
interrupt and assigns a priority to each interrupt based on the Interrupt
Vector Table (IVT) addressing scheme.
For more information, see “Inter-
rupt Vector Addresses” in Appendix B, Interrupt Vector Addresses.
The DSP supports three prioritized, individually-maskable external inter-
rupts, each of which can be either level- or edge-sensitive. External
interrupts occur when another device asserts one of the DSP’s interrupt
inputs (
IRQ2–0
). The DSP also supports internal interrupts. An internal
interrupt can stem from arithmetic exceptions, stack overflows, DMA
completion and/or peripheral data buffer status, or circular data buffer
overflows. Several factors control the DSP’s response to an interrupt. The
DSP responds to an interrupt request if:
• the DSP is executing instructions or is in an idle state.
• the interrupt is not masked.
• interrupts are globally enabled.
• a higher priority request is not pending.
When the DSP responds to an interrupt, the sequencer branches program
execution with a call to the corresponding interrupt vector address.
Within the DSP’s program memory, the interrupt vectors are grouped in
an area called the Interrupt Vector Table (IVT). The interrupt vectors in
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 ...