INTEL386 データシートの表示（PDF） - Intel

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INTEL386

Intel386 SX MICROPROCESSOR

Intel 

Intel386TM SX MICROPROCESSOR

Bit Position

0

1

2

3

31

Name

PE

MP

EM

TS

PG

Table 2 2 CR0 Definitions

Function

Protection mode enable places the Intel386 SX Microprocessor

into protected mode If PE is reset the processor operates again

in Real Mode PE may be set by loading MSW or CR0 PE can be

reset only by loading CR0 it cannot be reset by the LMSW

instruction

Monitor coprocessor extension allows WAIT instructions to

cause a processor extension not present exception (number 7)

Emulate processor extension causes a processor extension

not present exception (number 7) on ESC instructions to allow

emulating a processor extension

Task switched indicates the next instruction using a processor

extension will cause exception 7 allowing software to test

whether the current processor extension context belongs to the

current task

Paging enable bit is set to enable the on-chip paging unit It is

reset to disable the on-chip paging unit

2 2 Instruction Set

The instruction set is divided into nine categories of

operations

Data Transfer

Arithmetic

Shift Rotate

String Manipulation

Bit Manipulation

Control Transfer

High Level Language Support

Operating System Support

Processor Control

These instructions are listed in Table 9 1 Instruc-

tion Set Clock Count Summary

All Intel386 SX Microprocessor instructions operate

on either 0 1 2 or 3 operands an operand resides

in a register in the instruction itself or in memory

Most zero operand instructions (e g CLI STI) take

only one byte One operand instructions generally

are two bytes long The average instruction is 3 2

bytes long Since the Intel386 SX Microprocessor

has a 16 byte prefetch instruction queue an average

of 5 instructions will be prefetched The use of two

operands permits the following types of common in-

structions

Register to Register

Memory to Register

Immediate to Register

Memory to Memory

Register to Memory

Immediate to Memory

The operands can be either 8 16 or 32 bits long As

a general rule when executing code written for the

Intel386 SX Microprocessor (32-bit code) operands

are 8 or 32 bits when executing existing 8086 or

80286 code (16-bit code) operands are 8 or 16 bits

Prefixes can be added to all instructions which over-

ride the default length of the operands (i e use

32-bit operands for 16-bit code or 16-bit operands

for 32-bit code)

10

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