FAULTS
8-6
As indicated in
Figure 8-2
, two fault table entry types are allowed: local-call entry and system-call
entry. Each is two words in length. The entry type field (bits 0 and 1 of the entry’s first word) and
the value in the entry’s second word determine the entry type.
Other entry types (01
2
and 11
2
) are reserved and have unpredictable behavior.
To summarize, a fault handling procedure can be invoked through the fault table in any of three
ways: a local call, a system-local call or a system-supervisor call.
8.4
STACK USED IN FAULT HANDLING
The i960 architecture does not define a dedicated fault handling stack. Instead, to handle a fault,
the processor uses either the user, interrupt or supervisor stack, whichever is active when the fault
is generated. There is, however, one exception: if the user stack is active when a fault is generated
and the fault handling procedure is called with an implicit system supervisor call, the processor
switches to the supervisor stack to handle the fault.
8.5
FAULT RECORD
When a fault occurs, the processor records information about the fault in a fault record in memory.
The fault handling procedure uses the information in the fault record to correct or recover from the
fault condition and, if possible, resume program execution. The fault record is stored on the same
stack that the fault handling procedure will use to handle the fault.
local-call entry
(type 00
2
)
Provides an instruction pointer for the fault handling procedure. The
processor uses this entry to invoke the specified procedure by means of an
implicit local-call operation. The second word of a local procedure entry is
reserved. It must be set to zero when the fault table is created and not
accessed after that.
system-call entry
(type 10
2
)
Provides a procedure number in the system procedure table. This entry must
have an entry type of 10
2
and a value in the second word of 0000 027FH.
The processor computes the system procedure number by shifting right the
first word of the fault entry by two bit positions. Using this system procedure
number, the processor invokes the specified fault handling procedure by
means of an implicit call-system operation similar to that performed for the
calls
instruction.
Содержание i960 Jx
Страница 1: ...Release Date December 1997 Order Number 272483 002 i960 Jx Microprocessor Developer s Manual ...
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Страница 25: ...1 INTRODUCTION ...
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Страница 35: ...2 DATA TYPES AND MEMORY ADDRESSING MODES ...
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Страница 47: ...3 PROGRAMMING ENVIRONMENT ...
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Страница 73: ...4 CACHE AND ON CHIP DATA RAM ...
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Страница 85: ...5 INSTRUCTION SET OVERVIEW ...
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Страница 111: ...6 INSTRUCTION SET REFERENCE ...
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Страница 195: ...INSTRUCTION SET REFERENCE 6 83 6 Opcode mov 5CCH REG movl 5DCH REG movt 5ECH REG movq 5FCH REG See Also LOAD STORE lda ...
Страница 233: ...7 PROCEDURE CALLS ...
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Страница 257: ...8 FAULTS ...
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Страница 291: ...9 TRACING AND DEBUGGING ...
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Страница 309: ...10 TIMERS ...
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Страница 325: ...11 INTERRUPTS ...
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Страница 369: ...12 INITIALIZATION AND SYSTEM REQUIREMENTS ...
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Страница 413: ...13 MEMORY CONFIGURATION ...
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Страница 429: ...14 EXTERNAL BUS ...
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Страница 469: ...15 TEST FEATURES ...
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Страница 493: ...A CONSIDERATIONS FOR WRITING PORTABLE CODE ...
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Страница 503: ...B OPCODES AND EXECUTION TIMES ...
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Страница 515: ...C MACHINE LEVEL INSTRUCTION FORMATS ...
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Страница 523: ...D REGISTER AND DATA STRUCTURES ...
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Страница 551: ...GLOSSARY ...
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Страница 561: ...INDEX ...
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