MACHINE-LEVEL INSTRUCTION FORMATS
C-2
When a particular instruction is defined as not using a particular field, the field is ignored.
C.2
REG FORMAT
REG format is used for operations performed on data contained in registers. Most of the i960
processor family’s instructions use this format.
The opcode for the REG instructions is 12 bits long (three hexadecimal digits) and is split between
bits 7 through 10 and bits 24 through 31. For example, the
addi
opcode is 591H. Here, bits 24
through 31 contain 59H and bits 7 through 10 contain 1H.
src1 and src2 fields specify the instruction’s source operands. Operands can be global or local
registers or literals. Mode bits (M1 for src1 and M2 for src2) and the instruction type determine
what an operand specifies.
Table C-2
shows this relationship.
Table C-1. Instruction Field Descriptions
Instruction Field
Description
Opcode
The opcode of the instruction. Opcode encodings are defined in
section 6.1.8,
“Opcode and Instruction Format” (pg. 6-6)
.
src1
An input to the instruction. This field specifies a value or address. In one case of the
COBR format, this field is used to specify a register in which a result is stored.
src2
An input to the instruction. This field specifies a value or address.
src/dst
Depending on the instruction, this field can be (1) an input value or address, (2) the
register where the result is stored, or (3) both of the above.
abase
A register whose register’s value is used in computing a memory address.
INDEX
A register whose register’s value is used in computing a memory address.
displacement
A signed two’s complement number.
Offset
An unsigned positive number.
Optional
Displacement
A signed two’s complement number used in the two-word MEMB format.
MODE
A specification of how a memory address for an operand is computed and, for MEMB,
specifies whether the instruction contains a second word to be used as a
displacement.
SCALE
A specification of how a register’s contents are multiplied for certain addressing
modes (i.e., for indexing).
M1, M2, M3
These fields further define the meaning of the SRC 1, SRC 2, and
src/dst
fields
respectively as shown in and
Table C-3
.
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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