ADSP-2126x SHARC Processor Hardware Reference
1-7
Introduction
sequencer supply addresses for memory accesses. Together the sequencer
and data address generators allow computational operations to execute
with maximum efficiency since the computation units can be devoted
exclusively to processing data. With its instruction cache, the
ADSP-2126x can simultaneously fetch an instruction from the cache and
access two data operands from memory. The DAGs also provide built-in
support for zero-overhead circular buffering.
Program Sequencer.
The program sequencer supplies instruction
addresses to program memory. It controls loop iterations and evaluates
conditional instructions. With an internal loop counter and loop stack,
the ADSP-2126x executes looped code with zero overhead. No explicit
jump instructions are required to loop or to decrement and test the
counter. To achieve a high execution rate while maintaining a simple pro-
gramming model, the DSP employs a three stage pipeline to process
instructions—fetch, decode, and execute cycles.
Data Address Generators.
The DAGs provide memory addresses when
data is transferred between memory and registers. Dual data address gen-
erators enable the processor to output simultaneous addresses for two
operand reads or writes. DAG1 supplies 32-bit addresses for accesses using
the DM bus. DAG2 supplies 32-bit addresses for memory accesses over
the PM bus.
Each DAG keeps track of up to eight address pointers, eight address mod-
ifiers, and for circular buffering eight base-address registers and eight
buffer-length registers. A pointer used for indirect addressing can be mod-
ified by a value in a specified register, either before (pre-modify) or after
(post-modify) the access. A length value may be associated with each
pointer to perform automatic modulo addressing for circular data buffers.
The circular buffers can be located at arbitrary boundaries in memory.
Each DAG register has a secondary register that can be activated for fast
context switching.
Circular buffers allow efficient implementation of delay lines and other
data structures required in digital signal processing They are also
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 ...