ADSP-2126x SHARC Processor Hardware Reference
4-5
Data Address Generators
Circular Buffering Mode
The
CBUFEN
bit in the
MODE1
register enables circular buffering—a mode
where the DAG supplies addresses that range within a constrained buffer
length (set with an
L
register). Circular buffers start at a base address (set
with a
B
register), and increment addresses on each access by a modify
value (set with an
M
register).
The circular buffer enable bit (
CBUFEN
) in the
MODE1
register is
cleared (= 0) at reset. This makes the ADSP-2126x processor code
incompatible
with the ADSP-2106x SHARC family
(ADSP-21060/1/2 and ADSP-21065L) where circular buffering is
active upon reset. For code compatibility, programs ported to the
ADSP-2126x processors should include the instruction:
BIT SET MODE1 CBUFEN
.
For more information on setting up and using circular buffers, see
“Addressing Circular Buffers” on page 4-12
. When using circular buffers,
the DAGs can generate an interrupt on buffer overflow (wraparound). For
more information, see
“Using DAG Status” on page 4-9
.
Broadcast Loading Mode
The
BDCST1
and
BDCST9
bits in the
MODE1
register enable broadcast loading.
An example of broadcast loading is when a program uses one load com-
mand to load multiple registers. When the
BDCST1
bit is set (=1), the DAG
performs a dual data register load on instructions that use the
I1
register
for the address. The DAG loads both the named register (explicit register)
in one processing element and loads that register’s complementary register
(implicit register) in the other processing element. The
BDCST9
bit in the
MODE1
register enables this feature for the
I9
register.
Enabling either DAG register to perform a broadcast load has no effect on
register stores or loads to universal registers (
Uregs
). The one exception is
the register file data registers.
demonstrates the effects of a
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 ...