Compiled by

Venugopala Rao A SSr. Lecturer, Dept of CSE, SSE Mukka.

Microprocessors06CS45

8086 Family Assembler Language Programming CMP Destination, Source

Destination – Source (the result is not stored anywhere) Destination and Source operands can not be memory locations at

the same time It modifies flags AF CF OF PF SF ZF (if ZF is set, destination =

source) E.g. MOV AL, 5 MOV BL, 5 CMP AL, BL ; AL = 5, ZF = 1 (so equal!)

2 Venugopal Rao A S, SSE Mukka

8086 Family Assembler Language Programming MUL Source

Perform unsigned multiplication operation If source operand is a byte, AX = AL * Source If source operand is a word, (DX AX) = AX * Source Source operands can not be an immediate data It modifies CF and OF (AF,PF,SF,ZF undefined)E.g. MOV AL, 0C8h MOV BL, 4 MUL BL ; AX = 0320h (800)

3 Venugopal Rao A S, SSE Mukka

8086 Family Assembler Language Programming IMUL Source

Performs signed binary multiplication operation If source operand is a byte, AX = AL * Source If source operand is a word, (DX AX) = AX * Source Source operand can not be an immediate data It modifies CF and OF (AF,PF,SF,ZF undefined)E.g.

MOV AL, -2 MOV BL, -4 IMUL BL ; AX = 8

Try this in a program

4 Venugopal Rao A S, SSE Mukka

MOV AL, 20HMOV CL, 80HMUL CL

MOV AL, 20HMOV CL, 80HIMUL CL

8086 Family Assembler Language Programming DIV Source

Performs unsigned division operation If source operand is a byte, AL = AX / Source; AH = Remainder

of AX / Source If source operand is a word, AX=(DX AX)/Source;

DX=Remainder of (DX AX)/Source Source operands can not be an immediate dataE.g.

MOV AX, 00CBh MOV BL, 4 DIV BL ; AL = 50 (32h), AH = 3

5 Venugopal Rao A S, SSE Mukka

Examples: MOV AX, 5MOV BL, 2DIV BL

8086 Family Assembler Language Programming IDIV source

Performs signed division operation If source operand is a byte, AL = AX / Source; AH = Remainder

of AX / Source If source operand is a word, AX=(DX AX)/Source;

DX=Remainder of (DX AX)/Source Source operands can not be an immediate data E.g.

MOV AX, 0FF35h MOV BL, 4 IDIV BL ; AL = -50 (0CEh), AH = -3 (0FDh)

6 Venugopal Rao A S, SSE Mukka

Examples: MOV AL, -5MOV BL, 2IDIV BL

8086 Family Assembler Language Programming NEG destination

The result is represented in 2’s complementDestination can be a register or a memory locationIt modifies flags AF CF OF PF SF ZF E.g. MOV AL, 5 ; AL = 05h NEG AL ; AL = 0FBh (-5) NEG AL ; AL = 05h (5)

CBW Extends a signed 8-bit number in AL to a signed 16-bit data and stores it

into AX It does not modify flags

CWD Extends a signed 16-bit number in AX to a signed 32-bit data and stores it

into DX and AX. DX contains the most significant word It does not modify flags 7 Venugopal Rao A S, SSE Mukka

8086 Family Assembler Language Programming JMP Instructions:

Unconditional jumpIt moves microprocessor to execute another part of the program Target can be represented by a label, immediate data, registers, or memory

locations It does not affect flagsSimilar to Go To statements

Conditional JumpJump is based on some condition on flag register contents Similar to usage of if, if then else, while , do while etc

We can further classify JMP into two more classesIntersegment JMP Intrasegment JMP

8 Venugopal Rao A S, SSE Mukka

8086 Family Assembler Language Programming Intrasegment transfer v/sIntersegment transfer

Intrasegment transfer: the microprocessor jumps to an address within the same segment

Intersegment transfer: the microprocessor jumps to an address in a difference segment

Uses assembler directive near and far to indicate the types of JMP instructions

For intrasegment transfer, we can provide only new IP value in JMP instructions. E.g.: JMP 1000H

For intersegment transfer, we need provide both new CS and IP values in JMP instructions E.g.: JMP 2000H : 1000H

9 Venugopal Rao A S, SSE Mukka

8086 Family Assembler Language Programming Conditional JumpJZ Label_1

If ZF =1, jump to the target address labeled by Label_1; otherwise, do not jump

JNZ Label_1 If ZF =0, jump to the target address labeled by Label_1; otherwise,

do not jump Various other jump instruction:

10 Venugopal Rao A S, SSE Mukka

JNC JAE JNB JC JB JNAE JNGJNE JE JNS JS JNO JO JNPJPO JP JPE JA JBNE JBE JNAJGE JNL JL JNGE JG JNLE JLE