N386SX 데이터 시트보기 (PDF) - Intel

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N386SX

Intel387™ SX MATH COPROCESSOR

Intel 

Intel387TM SX MATH COPROCESSOR

3 0 PROGRAMMING INTERFACE

The Intel387 SX Math CoProcessor effectively ex-

tends to an Intel386 Microprocessor system addi-

tional instructions registers data types and inter-

rupts specifically designed to facilitate high-speed

floating point processing All communication be-

tween the CPU and the Math CoProcessor is trans-

parent to applications software The CPU automati-

cally controls the Math CoProcessor whenever a

numerics instruction is executed All physical memo-

ry and virtual memory of the CPU are available for

storage of the instructions and operands of pro-

grams that use the Math CoProcessor All memory

addressing modes including use of displacement

base register index register and scaling are avail-

able for addressing numerical operands

The Intel387 SX Math CoProcessor is software com-

patible with the Intel387 DX Math CoProcessors and

supports all applications written for the Intel386 CPU

and Intel387 Math CoProcessors

3 1 Instruction Set

The Intel386 CPU interprets the pattern 11011B in

most significant five bits of an instruction as an op-

code intended for a math coprocessor Instructions

thus marked are called ESCAPE or ESC instruction

The typical Math CoProcessor instruction accepts

one or two operands and produces one or some-

times two results In two-operand instructions one

operand is the contents of the Math CoProcessor

register while the other may be a memory location

The operands of some instructions are predefined

for example FSQRT always takes the square root of

the number in the top stack element

The Intel387 SX Math CoProcessor instruction set

can be divided into six groups The following sec-

tions gives a brief description of each instruction

Section 8 0 defines the instruction format and byte

fields Further details can be obtained from the

Intel387 User’s Manual Programmer’s Reference

Order 231917

3 1 1 DATA TRANSFER INSTRUCTIONS

The class includes the operations that load store

and convert operands of any support data types

Real Transfers

FLD Load Real (single double extended)

FST Store Real (single double)

FSTP Store Real and pop (single double ex-

tended)

FXCH Exchange registers

Integer Transfers

FILD Load (convert from) Integer (word short

long)

FIST Store (convert to) Integer (word short)

FISTP Store (convert to) Integer and pop (word

short long)

Packed Decimal Transfers

FBLD Load (convert from) packed decimal

FBSTP Store packed decimal and pop

3 1 2 ARITHMETIC INSTRUCTIONS

This class of instructions provide variations on the

basic add subtract multiply and divide operations

and a number of other basic arithmetic operations

Operands may reside in registers or one operand

may reside in memory

Addition

FADD

FADDP

FIADD

Add Real

Add Real and pop

Add Integer

Subtraction

FSUB Subtract Real

FSUBP Subtract Real and pop

FISUB Subtract Integer

FSUBR Subtract Real reversed

FSUBRP Subtract Real reversed and pop

FISUBR Subtract Integer reversed

Multiplication

FMUL Multiply Real

FMULP Multiply Real and pop

FIMUL Multiply Integer

Division

FDIV

FDIVP

FIDIV

FDIVR

FDIVRP

FIDIVR

Divide Real

Divide Real and pop

Divide Integer

Divide Real reversed

Divide Real reversed and pop

Divide Integer reversed

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