Mr. Vinod P. Tayade (M.Tech. VLSI Tech.)

Definition :Operand and Opcode

1/7/2021Mr. V. P. Tayade, Government Polyechnic, Nashik

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Operand – The data on which the operation is

performed called as operand

MOV A,R1 = A4h

BEFORE A = 20H & R1 = 30H – OPERAND

AFTER A = 30H & R1 = 30 H

Opcode (operational code) – The hexadecimal

code of an instruction is called as opcode.

Addressing Modes


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The Manner in which the operand is specified in an

instruction is called as addressing mode of that

instruction.

Types

Immediate Addressing Mode

Register Addressing Mode

Direct Addressing Mode

Register Indirect Addressing Mode

Immediate addressing mode


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In this Immediate Addressing Mode, the data is provided in theinstruction itself. The data is provided immediately after theOpcode. These are some examples of Immediate Addressing Mode.

MOV A, #0AFH ; A = AF

MOV R3, #45H ; R3 = 45h

MOV DPTR, #0FE00H ; DPTR = FE00H

In these instructions, the # symbol is used for immediate data. In thelast instruction, there is DPTR. The DPTR stands for Data Pointer.Using this, it points the external data memory location. In the firstinstruction, the immediate data is AFH, but one 0 is added at thebeginning. So when the data is starting with A to F, the data shouldbe preceded by 0.

Register addressing mode


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In the register addressing mode the source data

should be present in a register (R0 to R7). These are

some examples of Register Addressing Mode.

MOV A, R5

Before exe :- A=11h and R5=22h

After exe:- A=22h

MOV R0, A

Direct Addressing Mode


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In the Direct Addressing Mode, the source address is

specified by using 8-bit Address in an instruction. Only

the internal data memory can be used in this mode.

Here some of the examples of direct Addressing Mode.

MOV R2, 45H

Before :- R2=33h, 45h=44h

After :- R2=44h

MOV R0, 05H

MOV A, 20H

Register indirect addressing Mode


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In this mode, the source address is given in the registerand this register is represented in an instruction with asymbol ‘@’.

MOV A,@R1

R1 = 30 h & 30 h = 22h (before)

A = 22h

MOV A,#22H – Immediate A = 22h

MOV A,R1 - Register : R1=22h(Before) , A = 22h

MOV A,30H - Direct : 30h = 22 h , A = 22h

Operand = 22 H

Instruction Set


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TRANSFERARITHMETIC LOGICAL BOOLEAN

PROGRAM

BRANCHING

MOV ADD ANL CLR LJMP

MOVC ADDC ORL SETB AJMP

MOVX SUBB XRL MOV SJMP

PUSH INC CLR JC JZ

POP DEC CPL JNC JNZ

XCH MUL RL JB CJNE

XCHD DIV RLC JNB DJNZ

DA A RR JBC NOP

RRC ANL LCALL

SWAP ORL ACALL

CPL RET

RETI

JMP

Data Transfer Instructions


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The Data Transfer Instructions are associated with transfer with data between registers or external program memory or external data memory.

The Mnemonics associated with Data Transfer are given below.

MOV

MOVC

MOVX

PUSH

POP

XCH

XCHD



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Rough Work Slide


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MOV A,#33H A = 33H

MOV R0,A R0 = 33H

MOV 30H,R0 30H = 33H

MOV 33H,A 33H = 33H

MOV A,@R0 A = 33H

R0H =55H & R2H = 77H

A = R1=

MOV A,#55H & MOV R1,#77H

MOV A,30H & MOV R1,31H

MOV A,R0 & MOV R1,R2



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XCHD A,@R1

Before

A = 35 h

@R1 = 79h

After

A = 39h

@R1= 75h

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Mr. V. P. Tayade, Government Polyechnic, Nashik

Arithmetic Instructions


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Using Arithmetic Instructions, you can perform addition, subtraction, multiplicationand division. The arithmetic instructions also include increment by one, decrement byone and a special instruction called Decimal Adjust Accumulator.

The Mnemonics associated with the Arithmetic Instructions of the 8051Microcontroller Instruction Set are:

ADD

ADDC

SUBB

INC

DEC

MUL

DIV

DA A

The arithmetic instructions has no knowledge about the data format i.e. signed,unsigned, ASCII, BCD, etc. Also, the operations performed by the arithmeticinstructions affect flags like carry, overflow, zero, etc. in the PSW Register.



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DA A

DECIMAL ADJUST ACCUMULATOR AFTER ADDITION

IT CONVERTS INVALID BCD NUMBER IN TO THE VALID BCD NUMBER.

ADD A,R1

DA A

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Program: Write Assembly language program to perform addition of two 8-bit numbers, which are stored in 40H and 41H of internal memory. Store result in 42H.

ORG 0000H

MOV R0,#40H ;R0=40H

MOV A,@R0 ;A = 05H

INC R0 ; R0=41H

ADD A,@R0 ;A = 0CH

INC R0 ; R0 =42H

MOV @R0,A ;42H = 0CH

END

40h – 05h

41h – 07h

42h – 0Ch

43h – 00h

44h – 00h

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Program: Write Assembly language program to perform subtraction of two 8-bit numbers, which are stored in 50H and 51H of internal memory. Store result in 52H.

ORG 0000H

MOV R0,#50H ;R0=50H

MOV A,@R0 ; A = 15H

INC R0 ; R0=51H

SUBB A,@R0 ;A= 15-09-0

INC R0 ; R0 = 52H

MOV @R0,A ; 52H=A

END

50h – 15h

51h – 09h

52h – 00h

53h – 00h

54h – 00h

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Program: Write Assembly language program to perform multiplication of two 8-bit numbers, which are stored in 60H and 61H of external memory. Store result in 62H-LSB and 63H-MSB

ORG 0000H

MOV R0,#60H ;R0=60H

MOV A,@R0 ; A = 15H

MOV B,A ; B = 15H

INC R0 ; R0 =61H

MOV A,@R0 ; A = 09H

MUL AB ;A = LSB, B=MSB OV=?

INC R0 ;R0 = 62H

MOV @R0,A ; 62H = LSB OF RES

INC R0 ; R0 =63H

MOV A,B ; A = MSB OF RES

MOV @R0,A ; 64H = MSB OF RES

END

60h – 15h

61h – 09h

62h – 00h

63h – 00h

64h – 00h

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Program: Write Assembly language program to perform Division of two 8-bit numbers, which are stored in 0200H-(Divisor) and 0201H(Dividend) of external memory. Store result in 0202H-

Quotient and 0203H-Remainder

ORG 0000H

MOV DPTR,#0200H ; DPTR=0200H

MOVX A,@DPTR ;A = 02H

MOV B,A ;B = 02H

INC DPTR ;DPTR=0201H

MOVX A,@DPTR ;A=0BH

DIV AB ;A/B=A-Q, B=R,


MOVX @DPTR,A ;0202H=Q


MOV A,B ;A =REM

MOVX @DPTR,A ;0203=R

END

0200h – 02h

0201h – 0Bh

0202h – 00h

0203h – 00h

0204h – 00h

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Logical Instructions


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The next group of instructions are the Logical Instructions, which performlogical operations like AND, OR, XOR, NOT, Rotate, Clear and Swap.Logical Instruction are performed on Bytes of data on a bit-by-bit basis.

Mnemonics associated with Logical Instructions are as follows:

ANL

ORL

XRL

CLR

CPL

RL

RLC

RR

RRC

SWAP



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Boolean or Bit Manipulation Instructions


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As the name suggests, Boolean or Bit Manipulation Instructions will deal with bitvariables. We know that there is a special bit-addressable area in the RAM andsome of the Special Function Registers (SFRs) are also bit addressable.

The Mnemonics corresponding to the Boolean or Bit Manipulation instructions are:

CLR

SETB

MOV

JC

JNC

JB

JNB

JBC

ANL

ORL

CPL

Boolean or Bit Manipulation Instructions


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Program Branching Instructions


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The last group of instructions in the 8051 Microcontroller Instruction Set are the Program Branching Instructions. These

instructions control the flow of program logic. The mnemonics of the Program Branching Instructions are as follows.

LJMP

AJMP

SJMP

JZ

JNZ

CJNE

DJNZ

NOP

LCALL

ACALL

RET

RETI

JMP

All these instructions, except the NOP (No Operation) affect the Program Counter (PC) in one way or other. Some of these

instructions has decision making capability before transferring control to other part of the program.



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Instruction format


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Label(Optional) : Mnemonic destination,source

For example

L1 : MOV A,R1

Before execution / after

A = 22H / A = 44H

R1 = 44H / R1 = 44H

Mr. Vinod P. Tayade (M.Tech. VLSI Tech.) · 2021. 1. 7. · Arithmetic Instructions Mr. V. P....

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