THE 80286 INSTRUCTION SET

 

pp/n Instruction Byte Format

ModRM

 

 

 

"mod" Field Bit Assignments

mod

 

Displacement

00

OISP =

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

 

"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 value.

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

Figure B-1. In Instruction Byte Format

8-2

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Intel 80287, 80286 manual Instruction SET, Figure B-1. In Instruction Byte Format