PROGRAMMING ENVIRONMENT
3-20
Certain instructions, such as the branch-if instructions, use a 3-bit mask to evaluate the condition
code flags. For example, the branch-if-greater-or-equal instruction (
bge
) uses a mask of 011
2
to
determine if the condition code is set to either greater-than or equal. Conditional instructions use
similar masks for the remaining conditions such as: greater-or-equal (011
2
), less-or-equal (110
2
)
and not-equal (101
2
). The mask is part of the instruction opcode; the instruction performs a
bitwise AND of the mask and condition code.
The AC register integer overflow flag (bit 8) and integer overflow mask bit (bit 12) are used in
conjunction with the ARITHMETIC.INTEGER_OVERFLOW fault. The mask bit disables fault
generation. When the fault is masked and integer overflow is encountered, the processor sets the
integer overflow flag instead of generating a fault. When the fault is not masked, the fault is
allowed to occur and the flag is not set.
Once the processor sets this flag, the flag remains set until the application software clears it. Refer
to the discussion of the ARITHMETIC.INTEGER_OVERFLOW fault in
CHAPTER 8, FAULTS
for more information about the integer overflow mask bit and flag.
The no imprecise faults (AC.nif) bit (bit 15) determines whether or not faults are allowed to be
imprecise. When set, all faults are required to be precise; when clear, certain faults can be
imprecise. See
section 8.9, “PRECISE AND IMPRECISE FAULTS” (pg. 8-19)
for more infor-
mation. When set, the AC.nif bit disables the parallel instruction execution feature of the
processor; therefore, no imprecise faults mode should be invoked only during debugging when
maximum processor performance is not necessary.
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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