ADSP-2126x SHARC Processor Hardware Reference
4-17
Data Address Generators
There is one set of registers (
I7
and
I15
) in each DAG that can generate an
interrupt on circular buffer overflow (address wraparound).
information, see “Using DAG Status” on page 4-9.
When a program needs to use
I7
or
I15
without circular buffering and the
DSP has the circular buffer overflow interrupts unmasked, the program
should disable the generation of these interrupts by setting the
B7
/
B15
and
L7
/
L15
registers to values that prevent the interrupts from occurring. If
I7
were accessing the address range 0x1000 – 0x2000, the program could set
B7
= 0x0000 and
L7
= 0xFFFF. Because the DSP generates the circular
buffer interrupt based on the wraparound equations
, setting
the
L
register to zero does not necessarily achieve the desired results. If the
program is using either of the circular buffer overflow interrupts, it should
avoid using the corresponding
I
register(s) (
I7
or
I15
) where interrupt
branching is not needed.
There are two special cases to be aware of when using circular buffers.
1. In the case of circular buffer overflow interrupts, if
CBUFEN = 1
and
register
L7 = 0
(or
L15 = 0
), the
CB7I
(or
CB15I
) interrupt occurs at
every change of
I7
(or
I15
) after the index register (
I7
or
I15
)
crosses the base register (
B7
or
B15
) value. This behavior is indepen-
dent of the context of the DAG registers, both primary and
alternate.
2. When a LW access, SIMD access, or normal word access with the
LW option crosses the end of the circular buffer, the processor
completes the access before responding to the end of buffer
condition.
Modifying DAG Registers
The DAGs support two operations that modify an address value in an
index register without outputting an address. These two operations,
address bit-reversal and address modify, are useful for bit-reverse address-
ing and maintaining pointers.
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 ...