Mnemonics, Opcodes and Assembler Languages Rev792011

8/4/2019 Mnemonics, Opcodes and Assembler Languages Rev792011

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I NSTRUCTI ON SET,M ACH I NE CODE AND

ADDRESSI NG M ODEMNEM ONI CS, OPCODES ANDASSEM BLER LANGUAGES



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THE INSTRUCTION SET OF THE 8088/8086Data tr ansfer

instructionArithmeticinstruction

Logicinstruction

• t ransfers data

between memoryand registerswithin themicroprocessor orbetween int ernalregisters• ex: MOVinstruction

• performs

addition,subtraction,multiplication,divi sion, compareand othermathematicaloperations• ex: ADDinstruction

• performs logic

instructionsincluding AND,OR and XORinstructions• ex: RCLinstruction




THE INSTRUCTION SET OF THE 8088/8086Stringmanipulation

instruction

Controltransfer

instruction

Processorcontrol

instruction

• for al l thisinst ruct ion thememory source isDS:DI and thememory

dest inati on isES:DI• ex: CMPSinstruction

• decision makinggroup where adecision dependson a previousresul t such as a

mathematicaloutcome• ex: INTinstruction

• used to controlthe operat ion ofthe processor andset or clear thestatus indicators

• ex: HLTinstruction




SOFTWARE (INSTRUCTION)Op-code

ident i fies the operat ion t hat is to beperformed

Operand

the data that are to be processed




SOFTWARE (MACHINE CODE)

AddressOp-code

andoperand

Label Mnemonic Comments




SOFTWARE (MACHINE CODE)Address

Op-code andoperand

Label M nemonic Comments

Location ofthe op-code

and relateddata.

Hex code forinstruction

and relatedhex data.

A referencepoint given

a name tohelp relatethe programto a flowchart.

Manufacturers

mnemonicfor thatinstruction.

Anything tohelp

understandhow theprogramworks. Thesemicolonidentifiesthe start ofa comment .




ADDRESSING MODE 8088/8086Addressing mode:

Used to descr ibe the way a part icularinst ruct ion lets the microprocessorknow where the source or dest inat ion islocated

Method of speci fying an operand




ADDRESSING MODE 8088/8086The addressing modes are categor ized into

three types:

1. Register addressing mode

2. Immediate addressing mode

3. Memory addressing mode




ADDRESSING MODE 8088/8086Five memory addressing mode:

1. Di rect addressing mode

2.Register indi rect addressing mode

3. Based addressing mode

4. Indexed addressing mode

5. Based-indexed addressing mode




ADDRESSING MODE 8088/8086Register Addressing Mode

Register addressing is an addressingmode where the sour ce and thedest inat ion are both register .

Ex: M OV DS, AX ;copy AX int o DS




ADDRESSING MODE 8088/8086 Immediate Addressing Mode

Immediate addressing is the addressingmode where the requi red data(operand)is par t of t he inst ruct ion.

Ex: M OV AX, 1000H ;load AX wi th1000H




ADDRESSING MODE 8088/8086Di rect Addressing Mode

Di rect (absolut e, extended etc) is anaddressing mode where the operandspecifi es the sour ce or the dest inat ion.

Ex: M OV CX, [1234H ] ;move cont ent in1234H into CX




ADDRESSING MODE 8088/8086Register I ndirect Addressing Mode

Stor ing the memory address in apoint er or index register (SP,BP,SI ,orDI).

Ex: M OV [SI ],00FFH ;load data 00FFinto address that stored in SI




ADDRESSING MODE 8088/8086Based Addressing Mode

The effect ive address of the operand isobtained by adding a direct or indi rect

displacement to the cont ent s of ei therbase register BX or base point erregister BP

Ex: M OV [BX] + 1243H , AL




ADDRESSING MODE 8088/8086 I ndexed Addressing Mode

Use the value of displacement as apointer to the star t ing point of an array

of data in memory and t he cont ent s ofthe speci fied register as an index thatselect speci fi c element in t he array thatis to be accessed.

Ex: M OV AL, [SI ] + 2000H




ADDRESSING MODE 8088/8086Based-Indexed Addressing Mode

Use to access complex data st ructuressuch as two-dimensional array

Ex: M OV AH , [BX] [SI ] + 1234H

Mnemonics, Opcodes and Assembler Languages Rev792011

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