8086-2 datasheet(30/30 Pages) INTEL

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8086

Table 2. Instruction Set Summary

(Continued)

Mnemonic and

Instruction Code

Description

76543210

PROCESSOR CONTROL

CLC

e Clear Carry

11111000

CMC

e Complement Carry

11110101

STC

e Set Carry

11111001

CLD

e Clear Direction

11111100

STD

e Set Direction

11111101

CLI

e Clear Interrupt

11111010

STI

e Set Interrupt

11111011

HLT

e Halt

11110100

WAIT

e Wait

10011011

ESC

e Escape (to External Device)

1 1 0 1 1 x x x

mod x x x r/m

LOCK

e Bus Lock Prefix

11110000

NOTES:

e 8-bit accumulator

e 16-bit accumulator

e Count register

e Data segment

e Extra segment

Above/below refers to unsigned value

Greater

e more positive;

Less

e less positive (more negative) signed values

if d

e 1 then ‘‘to’’ reg; if d e 0 then ‘‘from’’ reg

if w

e 1 then word instruction; if w e 0 then byte instruc-

tion

if mod

e 11 then r/m is treated as a REG field

if mod

e 00 then DISP e 0*, disp-low and disp-high are

absent

if mod

e 01 then DISP e disp-low sign-extended to

16 bits, disp-high is absent

if mod

e 10 then DISP e disp-high; disp-low

if r/m

e 000 then EA e (BX) a (SI) a DISP

if r/m

e 001 then EA e (BX) a (DI) a DISP

if r/m

e 010 then EA e (BP) a (SI) a DISP

if r/m

e 011 then EA e (BP) a (DI) a DISP

if r/m

e 100 then EA e (SI) a DISP

if r/m

e 101 then EA e (DI) a DISP

if r/m

e 110 then EA e (BP) a DISP*

if r/m

e 111 then EA e (BX) a DISP

DISP follows 2nd byte of instruction (before data if re-

quired)

*except if mod e 00 and r/m e 110 then EA e disp-high;

disp-low.

if s w

e 01 then 16 bits of immediate data form the oper-

and

if s w

e 11 then an immediate data byte is sign extended

to form the 16-bit operand

if v

e 0 then ‘‘count’’ e 1; if v e 1 then ‘‘count’’ in (CL)

e don’t care

z is used for string primitives for comparison with ZF FLAG

SEGMENT OVERRIDE PREFIX

0 0 1 reg 1 1 0

REG is assigned according to the following table:

16-Bit (w

e 1)

8-Bit (w

e 0)

Segment

000

001

010

011

100

101

110

111

Instructions which reference the flag register file as a 16-bit

object use the symbol FLAGS to represent the file:

FLAGS

e X:X:X:X:(OF):(DF):(IF):(TF):(SF):(ZF):X:(AF):X:(PF):X:(CF)

DATA SHEET REVISION REVIEW

The following list represents key differences between this and the -004 data sheet. Please review this summa-

ry carefully.

1. The Intel 8086 implementation technology (HMOS) has been changed to (HMOS-III).

2. Delete all ‘‘changes from 1985 Handbook Specification’’ sentences.

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