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Volume 2, Part 1: Interruptions
The processor provides nested interrupt priority support for external interrupt vectors
0, 2, and 16 through 255 by:
• Automatically masking external interrupts of equal or lower priority than the
highest priority external interrupt currently in-service. This raises the in-service
external interrupt masking level when each external interrupt begins service by an
IVR read.
• Associating EOI writes with the highest priority in-service external interrupt, and
removing the in-service indication for this external interrupt. This lowers the
in-service masking level to that of the next highest priority currently in-service
external interrupt (if any).
This mechanism allows software external interrupt handlers to be interrupted by higher
priority external interrupts.
For example, assume software acquires an external interrupt vector 45 by reading IVR.
During the service of this interrupt other external interrupts can still be received and
are pended. If software sets PSR.i to a 1, pending external interrupts of equal or lower
priority than 45 are masked. However, a higher priority pending external interrupt can
be accepted by the processor (provided it is not masked by TPR.mmi or TPR.mic).
Assuming external interrupt vector 80 is received by the processor, the processor will
accept the interrupt by interrupting the control flow of the processor. During the service
of this interrupt, external interrupts of equal or lower priority than vector 80 are
masked. When EOI is issued by software, the processor will remove the in-service
indication for external interrupt vector 80. External interrupt masking will then revert
back to the next highest priority in-service external interrupt, vector 45. External
interrupt vectors of equal or lower priority than vector 45 would remain masked until
EOI is issued by software. The in-service indication for vector 45 is then removed by
the write to EOI.
5.8.2.1
Re-enabling External Interrupt Delivery
When emerging from code in which external interrupt delivery is disabled and
interruption state collection is turned off, the following minimal code sequence
describes the architectural method with which to re-enable interruption collection and
enable external interrupts:
ssm PSR.ic
// enable interruption collection
;;
srlz.d
// guarantee that interruption collection is enabled
ssm PSR.i
// enable external interrupts
The processor does not ensure that enabling external interrupts is immediately
observed after the
ssm
PSR.i instruction. Software must perform a data serialization
operation after
ssm
PSR.i to ensure that external interrupt delivery is enabled prior to a
given point in program execution.
5.8.2.2
External Interrupt Sampling
Assuming that external interrupt delivery is currently disabled (PSR.i is 0), the following
minimal code sequence describes the architectural method with which to briefly open
the external interrupt window for external interrupt sampling (typically PSR.ic is 1 to
enable interruption collection):
Summary of Contents for ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS VOLUME 3 REV 2.3
Page 1: ......
Page 11: ...x Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 13: ...1 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 33: ...1 22 Volume 1 Part 1 Introduction to the Intel Itanium Architecture ...
Page 57: ...1 46 Volume 1 Part 1 Execution Environment ...
Page 147: ...1 136 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 149: ...1 138 Volume 1 Part 2 About the Optimization Guide ...
Page 191: ...1 180 Volume 1 Part 2 Predication Control Flow and Instruction Stream ...
Page 230: ......
Page 248: ...236 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 250: ...2 2 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 264: ...2 16 Volume 2 Part 1 Intel Itanium System Environment ...
Page 380: ...2 132 Volume 2 Part 1 Interruptions ...
Page 398: ...2 150 Volume 2 Part 1 Register Stack Engine ...
Page 486: ...2 238 Volume 2 Part 1 IA 32 Interruption Vector Descriptions ...
Page 750: ...2 502 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 754: ...2 506 Volume 2 Part 2 About the System Programmer s Guide ...
Page 796: ...2 548 Volume 2 Part 2 Interruptions and Serialization ...
Page 808: ...2 560 Volume 2 Part 2 Context Management ...
Page 842: ...2 594 Volume 2 Part 2 Floating point System Software ...
Page 850: ...2 602 Volume 2 Part 2 IA 32 Application Support ...
Page 862: ...2 614 Volume 2 Part 2 External Interrupt Architecture ...
Page 870: ...2 622 Volume 2 Part 2 Performance Monitoring Support ...
Page 891: ......
Page 1099: ...3 200 Volume 3 Instruction Reference padd Interruptions Illegal Operation fault ...
Page 1295: ...3 396 Volume 3 Resource and Dependency Semantics ...
Page 1296: ......
Page 1302: ...402 Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1494: ...4 192 Volume 4 Base IA 32 Instruction Reference FWAIT Wait See entry for WAIT ...
Page 1647: ...Volume 4 Base IA 32 Instruction Reference 4 345 ROL ROR Rotate See entry for RCL RCR ROL ROR ...
Page 1884: ...4 582 Volume 4 IA 32 SSE Instruction Reference ...
Page 1885: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 Index ...
Page 1886: ...Index Intel Itanium Architecture Software Developer s Manual Rev 2 3 ...
Page 1898: ...INDEX Index 12 Index for Volumes 1 2 3 and 4 ...