ADSP-2126x SHARC Processor Hardware Reference
4-9
Data Address Generators
Using DAG Status
The DAGs can provide addressing for a constrained range of addresses,
repeatedly cycling through this data (or buffer). A buffer overflow (or
wraparound) occurs each time the DAG circles past the buffer’s base
address. (See
“Addressing Circular Buffers” on page 4-12
.)
The DAGs can provide buffer overflow information when executing circu-
lar buffer addressing for the
I7
or
I15
registers. When a buffer overflow
occurs (a circular buffering operation increments the
I
register past the
end of the buffer), the appropriate DAG updates a buffer overflow flag in
a sticky status (
STKYx
) register. A buffer overflow can also generate a mas-
kable interrupt. Two ways to use buffer overflows from circular buffering
are:
•
Interrupts.
Enable interrupts and use an interrupt service routine
(ISR) to handle the overflow condition immediately. This method
is appropriate if it is important to handle all overflows as they
occur; for example in a “ping-pong” or swap I/O buffer pointers
routine.
•
STKYx registers.
Use the
BIT
TST
instruction to examine overflow
flags in the
STKY
register after a series of operations. If an overflow
flag is set, the buffer has overflowed—wrapped around—at least
once. This method is useful when overflow handling is not time
sensitive.
DAG Operations
The DSP’s DAGs perform several types of operations to generate data
addresses. As shown in
MODE1
,
MODE2
, and
STKYx
registers all contribute to DAG operations. The follow-
ing sections provide details on DAG operations:
Содержание ADSP-21261 SHARC
Страница 30: ...Contents xxx ADSP 2126x SHARC Processor Hardware Reference ...
Страница 40: ...Register Diagram Conventions xl ADSP 2126x SHARC Processor Hardware Reference ...
Страница 58: ...Differences From Previous SHARCs 1 18 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 112: ...Secondary Processing Element PEy 2 54 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 178: ...Summary 3 66 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 204: ...DAG Instruction Summary 4 26 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 322: ...Setting Up DMA 7 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 436: ...SPORT Programming Examples 9 86 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 521: ...ADSP 2126x SHARC Processor Hardware Reference 11 31 Input Data Port rts IDP_ISR end ...
Страница 522: ...Input Data Port Programming Example 11 32 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 590: ...Timer Programming Examples 14 20 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 796: ...I O Processor Registers A 174 ADSP 2126x SHARC Processor Hardware Reference ...
Страница 800: ...B 4 ADSP 2126x SHARC Processor Core Manual ...
Страница 846: ...Index I 36 ADSP 2126x SHARC Processor Hardware Reference ...