Datasheet

ADSP-21477/ADSP-21478/ADSP-21479
Rev. C | Page 5 of 76 | July 2013
buses and on-chip instruction cache, the processor can simulta-
neously fetch four operands (two over each data bus) and one
instruction (from the cache), all in a single cycle.
Instruction Cache
The processor includes an on-chip instruction cache that
enables three-bus operation for fetching an instruction and four
data values. The cache is selective—only the instructions whose
fetches conflict with PM bus data accesses are cached. This
cache allows full speed execution of core looped operations such
as digital filter multiply-accumulates, and FFT butterfly
processing.
Data Address Generators with Zero-Overhead Hardware
Circular Buffer Support
The processor’s two data address generators (DAGs) are used
for indirect addressing and implementing circular data buffers
in hardware. Circular buffers allow efficient programming of
delay lines and other data structures required in digital signal
processing, and are commonly used in digital filters and Fourier
transforms. The two DAGs of the processors contain sufficient
registers to allow the creation of up to 32 circular buffers (16
primary register sets, 16 secondary). The DAGs automatically
handle address pointer wraparound, reduce overhead, increase
performance, and simplify implementation. Circular buffers can
start and end at any memory location.
Flexible Instruction Set
The 48-bit instruction word accommodates a variety of parallel
operations, for concise programming. For example, the
processors can conditionally execute a multiply, an add, and a
subtract in both processing elements while branching and fetch-
ing up to four 32-bit values from memory—all in a single
instruction.
Variable Instruction Set Architecture (VISA)
In addition to supporting the standard 48-bit instructions from
previous SHARC processors, the processors support new
instructions of 16 and 32 bits. This feature, called Variable
Instruction Set Architecture (VISA), drops redundant/unused
Figure 2. SHARC Core Block Diagram
S
SIMD Core
CACHEINTERRUPT
5 STAGE
PROGRAM SEQUENCER
PM ADDRESS 32
DM ADDRESS 32
DM DATA 64
PM DATA 64
DAG1
16×32
MRF
80-BIT
ALU
MULTIPLIER
SHIFTER
RF
Rx/Fx
PEx
16×40-BIT
JTAG
DMD/PMD 64
ASTATx
STYKx
ASTATy
STYKy
TIMER
RF
Sx/SFx
PEy
16×40-BIT
MRB
80-BIT
MSB
80-BIT
MSF
80-BIT
FLAG
SYSTEM
I/F
USTAT
4×32-BIT
PX
64-BIT
DAG2
16×32
ALU
MULTIPLIER
SHIFTER
DATA
SWAP
PM ADDRESS 24
PM DATA 48