Intel 80287 manual 80286 U\lSTRUCTION SET, Figure B-2 Ir Instruction Byte Format

Models: 80287 80286

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THE 80286 U\lSTRUCTION SET

Ir Instruction Byte Format

 

"mod" Field Bit Assignments

mod

 

Displacement

00

DISP -

0(2), disp-Iow and disp-high are absent

01

OISP -

disp-Iow sign-extended to 16-bits, disp-high is absent

10OISP - disp-high; disp-Iow

11rIm is treated as a "reg" field

 

 

"r" Field Bit Assignments

 

16-Blt (w - 1)

B-Blt (w - 0)

Segment

000 AX

000 AL

00 ES

001

CX

001 CL

01 CS

010

OX

010 OL

10 SS

011

BX

011 BL

11 OS

100

SP

100 AH

 

101

BP

101 CH

 

110

SI

1100H

 

111

01

111 BH

 

 

"rim" Field Bit Assignments

rim

Operand Address

000

(BX) + (SI) + OISP

001

(BX) + (01) + OISP

010

(BP) + (SI) + OISP

'011

(BP) + (01) + OISP

100

(SI) +OISP

101

(01) + OISP

110

(BP) + 0ISP(2)

111

(BX) + OISP

OISP follows 2nd byte of ,instruction (before data if required).

NOTES:

,,1. Opcode indicates presence and size of immediate field.

2.Except If mod-OO and r/m-110then EA-disp-high: disp-Iow.

Figure B-2_ Ir Instruction Byte Format

8-4

Page 214
Image 214
Intel 80287 manual 80286 U\lSTRUCTION SET, Figure B-2 Ir Instruction Byte Format