ADSP-2126x SHARC Processor Hardware Reference
3-57
Program Sequencer
push occurs when the stack is already full. Bits in the
STKYx
register indi-
cate the status stack full and empty states as describe below.
•
Status stack overflow.
Bit 23 (
SSOV
) indicates that the status stack
is overflowed (if 1) or not overflowed (if 0)—a sticky bit.
•
Status stack empty.
Bit 24 (
SSEM
) indicates that the status stack is
empty (if 1) or not empty (if 0)—not sticky, cleared by a
PUSH
.
For some interrupts, (
IRQ2–0
and timer expired), the sequencer automati-
cally pushes the
ASTATx
,
ASTATy
, and
MODE1
registers onto the status stack.
When the sequencer pushes an entry onto the status stack, the DSP uses
the
MMASK
register to clear the corresponding bits in the
MODE1
register. All
other bit settings remain the same. For more information and an example
of how the
MMASK
and
MODE1
registers work together, see
The sequencer automatically pops the
ASTATx
,
ASTATY
, and
MODE1
registers
from the status stack during the return from interrupt instruction (
RTI
).
In one other case,
JUMP
(
CI
), the sequencer pops the stack.
mation, see “Reusing Interrupts” on page 3-60.
IRQ2–0
and
timer expired interrupts cause the sequencer to push an entry onto the sta-
tus stack. All other interrupts require either explicit saves and restores of
effected registers or an explicit push or pop of the stack (
PUSH
/
POP
STS
).
Pushing the
ASTATx
,
ASTATy
, and
MODE1
registers preserves the status and
control bit settings. This allows a service routine to alter these bits with
the knowledge that the original settings are automatically restored upon
the return from the interrupt.
The top of the status stack contains the current values of
ASTATx
,
ASTATy
,
and
MODE1
. Reading and writing these registers does not move the stack
pointer. Explicit
PUSH
or
POP
instructions do move the status stack pointer.
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 ...