FAULTS
8-12
A fault that occurs during any of the above actions is called an override fault. In response to this
condition, the processor does the following:
•
Switches the execution mode to supervisor.
•
Selects the override condition that shows that the writing of the fault record was unsuccessful.
If no such fault exists, the processor selects one of the other fault conditions. This method
ensures that the fault handler has information regarding the fault record write.
•
Saves information pertaining to the override condition selected. The fault record describes the
first fault as described previously. Field OType contains the fault type of the second fault, field
OSubtype contains the fault subtype of the second fault and field override-fault-data contains
what would normally be the fault data field for the second fault type.
•
Attempts to access the IP of the first instruction in the override fault handler through the
system procedure table.
It should be noted that a fault that occurs while the processor is actually executing a fault handling
procedure is not an override fault.
The override fault entry is entry 0. If the override fault entry in the fault table points to a location
beyond the system procedure table, the processor enters system error mode. Override fault
conditions include: PROTECTION and OPERATION.UNIMPLEMENTED faults.
An override fault handler must be accessed through a system-supervisor call. Local and
system-local override fault handlers are not supported by the architecture and have an
unpredictable behavior. Tracing is disabled upon entry into the override fault handler (PC.te is
cleared). It is restored upon return from the handler. To prevent infinite internal loops, the override
fault handler should not set PC.te.
8.6.6
System Error
If a fault is detected while the processor is in the process of servicing an override or parallel fault,
the processor enters the system error state. Note that “servicing” indicates that the processor has
detected the override or parallel fault, but has not begun executing the fault handling procedure.
This type of error causes the processor to enter a system error state. In this state, the processor uses
only one read bus transaction to signal the fail code message; the address of the bus transaction is
the fail code itself.
8.7
FAULT HANDLING PROCEDURES
The fault handling procedures can be located anywhere in the address space except within the
on-chip data RAM or MMR space. Each procedure must begin on a word boundary. The processor
can execute the procedure in user or supervisor mode, depending on the fault table entry type.
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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