INTEL386 Просмотр технического описания (PDF) - Intel

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INTEL386

Intel386 SX MICROPROCESSOR

Intel 

Intel386TM SX MICROPROCESSOR

Function

Interrupt table limit

too small

CS DS ES FS GS

Segment overrun exception

SS Segment overrun

exception

Table 3 1 Exceptions in Real Mode

Interrupt

Number

Related

Instructions

8

INT vector is not

within table limit

13

Word memory reference

with offset e 0FFFFH

an attempt to execute

past the end of CS segment

12

Stack Reference

beyond offset e 0FFFFH

Return

Address Location

Before

Instruction

Before

Instruction

Before

Instruction

3 2 Reserved Locations

There are two fixed areas in memory which are re-

served in Real address mode the system initializa-

tion area and the interrupt table area Locations

00000H through 003FFH are reserved for interrupt

vectors Each one of the 256 possible interrupts has

a 4-byte jump vector reserved for it Locations

0FFFFF0H through 0FFFFFFH are reserved for sys-

tem initialization

3 3 Interrupts

Many of the exceptions discussed in section 2 7 are

not applicable to Real Mode operation in particular

exceptions 10 11 and 14 do not occur in Real

Mode Other exceptions have slightly different

meanings in Real Mode Table 3 1 identifies these

exceptions

3 4 Shutdown and Halt

The HLT instruction stops program execution and

prevents the processor from using the local bus until

restarted Either NMI FLT INTR with interrupts

enabled (IFe1) or RESET will force the Intel386 SX

Microprocessor out of halt If interrupted the saved

CS IP will point to the next instruction after the HLT

Shutdown will occur when a severe error is detected

that prevents further processing In Real Mode

shutdown can occur under two conditions

1 An interrupt or an exception occurs (Exceptions 8

or 13) and the interrupt vector is larger than the

Interrupt Descriptor Table

2 A CALL INT or PUSH instruction attempts to

wrap around the stack segment when SP is not

even

An NMI input can bring the processor out of shut-

down if the Interrupt Descriptor Table limit is large

enough to contain the NMI interrupt vector (at least

000FH) and the stack has enough room to contain

the vector and flag information (i e SP is greater that

0005H) Otherwise shutdown can only be exited by

a processor reset

3 5 LOCK Operation

The LOCK prefix on the Intel386 SX Microprocessor

even in Real Mode is more restrictive than on the

80286 This is due to the addition of paging on the

Intel386 SX Microprocessor in Protected Mode and

Virtual 8086 Mode The LOCK prefix is not support-

ed during repeat string instructions

The only instruction forms where the LOCK prefix is

legal on the Intel386 SX Microprocessor are shown

in Table 3 2

Table 3 2 Legal Instructions for the LOCK Prefix

Opcode

Operands

(Dest Source)

BIT Test and

SET RESET

COMPLEMENT

Mem Reg Immediate

XCHG

Reg Mem

XCHG

Mem Reg

ADD OR ADC SBB

AND SUB XOR

Mem Reg Immediate

NOT NEG INC DEC Mem

An exception 6 will be generated if a LOCK prefix is

placed before any instruction form or opcode not

listed above The LOCK prefix allows indivisible

read modify write operations on memory operands

using the instructions above

The LOCK prefix is not IOPL-sensitive on the

Intel386 SX Microprocessor The LOCK prefix can

be used at any privilege level but only on the in-

struction forms listed in Table 3 2

23

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