complicated analysis

8086-80486 – Inst
Set & ALP
MOV Revisted

EX 1. Swap the word at memory location
24000H with 25000H

24000H

24001H

25000H
25001H

MOV AX, 2000H

•

Initialise Segment
Register

•

Initialise Offset Registers

•

Transfer data from reg to mem temporarily

•

Store back the data in mem MOV DS, AX

MOV SI, 4000H
MOV DI, 5000H
MOV BX, [SI]
MOV DX, [DI]
MOV [SI], DX
MOV [DI], BX

Ex 2
MOV BX, 2000H
MOV DI, 10H
MOV AL, [BX+DI]

MOV DI, 20H
MOV [BX+DI], AL

DS: 2020  DS: 2010

Different mov options
R



M

M



R

R



R

M



I

R



I

MOV

DST,SRC

•

Copies the contents of source to destination

•

No Flags Affected

•

Size of source and destination must be the same

•

Source can be register, memory, or immediate data

•

Destination can be register or memory location

Types of Instruction
●
●
●
●

Data Transfer Instructions
Arithmetic Instructions
Logical Instructions
Branch and Program control Instructions

8086-80486 – Inst
Set & ALP
A Simple Program

INC Destination
•

Destination – Register or memory location ( specified in 24 diff ways)

•

( AF, OF, PF, SF, ZF affected, CF not affected)

•

INC BL

•

INC BX

•

DEC Destination

Inc / Dec the contents of a
Memory location
•

Specify the data size in memory

•

use directive

•

BYTE PTR, WORD PTR, DWORD PTR

•

INC WORD PTR [BX]

•

INC BYTE PTR[BX]

•

BX-1000H DS- 2000H

21000
21000

FF
00

21001
21001

00
00
01

Flags
INC WORD PTR [BX]

INC BYTE PTR[BX]

•

OF – 0

•

OF – 0

•

SF – 0

•

SF – 0

•

ZF - 0

•

ZF -1

•

PF – 1(follows only low byte)

•

PF -1

•

AF - 1

•

AF -1

Branch Instructions
JE/JZ

Displacement (-128 to +127)

JNE/ JNZ

Displacement (-128 to +127)

Copy a block of data from one memory area to another memory area- from