Micro Controller 8051- Soft

8/2/2019 Micro Controller 8051- Soft

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Numerical Bases Used in Programming

Hexadecimal

Binary

BCD


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Hexadecimal Basis

Hexadecimal Digits:

1 2 3 4 5 6 7 8 9 A B C D E F

A=10

B=11

C=12D=13

E=14

F=15


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Decimal, Binary, BCD, & Hexadecimal Numbers

(43)10=

(0100 0011)BCD=

( 0010 1011 )2 =

( 2 B )16


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Registers

A

B

R0

R1

R3

R4

R2

R5

R7

R6

DPH DPL

PC

DPTR

PC

Some 8051 16-bit Register

Some 8-bitt Registers of

the 8051

SP


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Memory mapping in 8051

ROM memory map in 8051 family

0000H

0FFFH

0000H

1FFFH8751

AT89C518752

AT89C52

4k 8k


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RAM memory space allocation in the 8051

7FH

30H

2FH

20H

1FH

17H

10H

0FH

07H

08H

18H

00HRegister Bank 0

(Stack) Register Bank 1

Register Bank 2

Register Bank 3

Bit-Addressable RAM

Scratch pad RAM


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Addressing Modes

Register

Direct

Register Indirect

Immediate

Relative

Absolute

Long Indexed


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Register Addressing Mode

MOVRn, A ;n=0,..,7

ADD A, Rn

MOVDPL, R6

MOVDPTR, A

MOVRm, Rn


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Direct Addressing Mode

Although the entire of 128 bytes of RAM can beaccessed using direct addressing mode, it is mostoften used to access RAM loc. 30 7FH.

MOVR0, 40H

MOV56H, A

MOVA, 4 ; MOV A, R4

MOV6, 2 ; copy R2 to R6

; MOV R6,R2 is invalid !


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Register Indirect Addressing Mode

In this mode, register is used as a pointer to thedata.

MOV A,@Ri ; move content of RAM loc.where address is held by Ri into A ( i=0 or 1 )

MOV @R1,B

In other word, the content of register R0 or R1 issources or target in MOV, ADD and SUBBinsructions.


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Immediate Addressing Mode

MOVA,#65H

MOVR6,#65H

MOVDPTR,#2343H

MOVP1,#65H


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Relative, Absolute, & Long Addressing

Used only with jump and call instructions:

SJMP

ACALL,AJMP

LCALL,LJMP


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Indexed Addressing Mode

This mode is widely used in accessing dataelements of look-up table entries located in theprogram (code) space ROM at the 8051

MOVC A,@A+DPTR (A,@A+PC)

A= content of address A +DPTR from ROM

Note:

Because the data elements are stored in theprogram (code ) space ROM of the 8051, it usesthe instruction MOVC instead of MOV. TheC means code.


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SomeSimple Instructions

MOV dest,source ; dest = source

MOV A,#72H ;A=72H

MOV R4,#62H ;R4=62H

MOV B,0F9H ;B=the content of F9th byte of RAM

MOV DPTR,#7634H

MOV DPL,#34HMOV DPH,#76H

MOV P1,A ;mov A to port 1

Note 1:

MOV A,#72H MOV A,72HAfter instruction MOV A,72H the content of 72th byte of RAM willreplace in Accumulator.

Note 2:MOV A,R3 MOV A,3


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ADDA, Source ;A=A+SOURCE

ADDA,#6 ;A=A+6

ADDA,R6 ;A=A+R6

ADD A,6 ;A=A+[6] or A=A+R6

ADD A,0F3H ;A=A+[0F3H]

SUBB A, Source ;A=A-SOURCE-C

SUBB A,#6 ;A=A-6

SUBB A,R6 ;A=A+R6


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MUL & DIV

MUL AB ;B|A = A*BMOV A,#25H

MOV B,#65H

MUL AB ;25H*65H=0E99

;B=0EH, A=99H

DIV AB ;A = A/B, B = A mod B

MOV A,#25MOV B,#10

DIV AB ;A=2, B=5


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SETB bit ; bit=1

CLR bit ; bit=0

SETB C ; CY=1

SETB P0.0 ;bit 0 from port 0 =1

SETB P3.7 ;bit 7 from port 3 =1

SETB ACC.2 ;bit 2 from ACCUMULATOR =1

SETB 05 ;set high D5 of RAM loc. 20h

Note:

CLR instruction is as same as SETB

i.e.:

CLR C ;CY=0

But following instruction is only for CLR:

CLR A ;A=0


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DEC byte ;byte=byte-1

INC byte ;byte=byte+1

INC R7

DEC A

DEC 40H ; [40]=[40]-1


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RR RL RRC RLC A

EXAMPLE:RR A

RR:

RRC:

RL:

RLC:

C

C


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ANL - ORL XRL

Bitwise Logical Operations:AND, OR, XOREXAMPLE:

MOV R5,#89H

ANLR5,#08H

CPL A ;1s complementExample:

MOV A,#55H ;A=01010101 B

L01: CPL A

MOV P1,A

ACALL DELAY

SJMP L01


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Stack in the 8051 The register used to

access the stack is calledSP (stack pointer)register.

The stack pointer in the8051 is only 8 bits wide,

which means that it cantake value 00 to FFH.When 8051 powered up,the SP register containsvalue 07.

7FH

30H

2FH

20H

1FH

17H

10H

0FH

07H

08H

18H

00HRegister Bank 0

(Stack) Register Bank 1

Register Bank 2

Register Bank 3

Bit-Addressable RAM

Scratch pad RAM


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Example:

MOV R6,#25H

MOV R1,#12H

MOV R4,#0F3H

PUSH 6

PUSH 1

PUSH 4

0BH

0AH

09H

08H

Start SP=07H

25

0BH

0AH

09H

08H

SP=08H

F3

12

25

0BH

0AH

09H

08H

SP=08H

12

25

0BH

0AH

09H

08H

SP=09H


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LOOP and JUMP Instructions

JZ Jump if A=0

JNZ Jump if A/=0

DJNZ Decrement and jump if A/=0

CJNE A,byte Jump if A/=byte

CJNE reg,#data Jump if byte/=#data

JC Jump if CY=1

JNC Jump if CY=0

JB Jump if bit=1

JNB Jump if bit=0

JBC Jump if bit=1 and clear bit

Conditional Jumps :


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DJNZ:

Write a program to clear ACC, thenadd 3 to the accumulator ten time

Solution:

MOV A,#0

MOV R2,#10

AGAIN: ADD A,#03

DJNZ R2,AGAIN ;repeat until R2=0 (10 times)

MOV R5,A


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LJMP(long jump)

LJMP is an unconditional jump. It is a 3-byte instruction.

It allows a jump to any memory location from 0000 toFFFFH.

AJMP(absolute jump)

In this 2-byte instruction, It allows a jump to any memorylocation within the 2k block of program memory.

SJMP(short jump)

In this 2-byte instruction. The relative address range of 00-

FFH is divided into forward and backward jumps, that is ,within -128 to +127 bytes of memory relative to the addressof the current PC.


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CALL InstructionsAnother control transfer instruction is the CALL

instruction, which is used to call a subroutine.

LCALL(long call)

This 3-byte instruction can be used to call

subroutines located anywhere within the 64K

byte address space of the 8051.

ACALL (absolute call)

ACALL is 2-byte instruction. the targetaddress of the subroutine must be within 2Kbyte range.


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Example:

Write a program to copy a block of 10 bytes from RAMlocation starting at 37h to RAM location starting at 59h.

Solution:

MOV R0,#37h ; source pointer

MOV R1,#59h ; dest pointer

MOV R2,#10 ; counter

L1: MOV A,@R0

MOV @R1,A

INC R0INC R1

DJNZ R2,L1


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Performing the Addition with 8051

. 65536's 256's 1's

. R6 R7

+ R4 R5

= R1 R2 R3

1.Add the low bytes R7 and R5, leave the answer in R3.

2.Add the high bytes R6 and R4, adding any carry from step 1, and leave the answer in R2.

3.Put any carry from step 2 in the final byte, R1.


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Steps 1, 2, 3

MOV A,R7 ;Move the low-byte into the accumulator

ADD A,R5 ;Add the second low-byte to the accumulator

MOV R3,A ;Move the answer to the low-byte of the result

MOV A,R6 ;Move the high-byte into the accumulator

ADDC A,R4 ;Add the second high-byte to the accumulator, plus carry.

MOV R2,A ;Move the answer to the high-byte of the result

MOV A,#00h ;By default, the highest byte will be zero.

ADDC A,#00h ;Add zero, plus carry from step 2.

MOV R1,A ;Move the answer to the highest byte of the result


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The Whole Program;Load the first value into R6 and R7

MOV R6,#1Ah

MOV R7,#44h;Load the first value into R4 and R5

MOV R4,#22h

MOV R5,#0DBh

;Call the 16-bit addition routine LCALL ADD16_16

ADD16_16:

;Step 1 of the processMOV A,R7 ;Move the low-byte into the accumulator

ADD A,R5 ;Add the second low-byte to the accumulator

MOV R3,A ;Move the answer to the low-byte of the result

;Step 2 of the process

MOV A,R6 ;Move the high-byte into the accumulator

ADDC A,R4 ;Add the second high-byte to the accumulator, plus carry.

MOV R2,A ;Move the answer to the high-byte of the result

;Step 3 of the process

MOV A,#00h ;By default, the highest byte will be zero.

ADDC A,#00h ;Add zero, plus carry from step 2.

MOV MOV R1,A ;Move the answer to the highest byte of the result

;Return - answer now resides in R1, R2, and R3. RET


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Timer & Port Operations

Example:

Write a program using Timer0 to create a 10khz squarewave on P1.0

MOV TMOD,#02H ;8-bit auto-reload modeMOV TH0,#-50 ;-50 reload value in TH0

SETB TR0 ;start timer0

LOOP: JNB TF0, LOOP ;wait for overflow

CLR TF0 ;clear timer0 overflow flag

CPL P1.0 ;toggle port bit

SJMP LOOP ;repeat

END


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Interrupts

1. Enabling and Disabling Interrupts

2. Interrupt Priority

3. Writing the ISR (Interrupt Service

Routine)


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Interrupt Enable (IE) Register :

EA : Global enable/disable.

--- : Undefined.

ET2 :Enable Timer 2 interrupt.

ES :Enable Serial port interrupt.

ET1 :Enable Timer 1 interrupt.

EX1 :Enable External 1 interrupt. ET0 : Enable Timer 0 interrupt.

EX0 : Enable External 0 interrupt.


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Interrupt Vectors

Interrupt Vector Address

System Reset 0000H

External 0 0003H

Timer 0 000BH

External 1 0013H

Timer 1 001BH

Serial Port 0023HTimer 2 002BH


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Writing the ISRExample:

Writing the ISR for Timer0 interrupt

ORG 0000H ;reset

LJMP MAIN

ORG 000BH ;Timer0 entry point

T0ISR: . ;Timer0 ISR begins

.

RETI ;return to main program

MAIN: . ;main program

.

.

END


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Structure of Assembly language and

Running an 8051 program

EDITOR

PROGRAM

ASSEMBLER

PROGRAM

LINKER

PROGRAM

OH

PROGRAM

Myfile.asm

Myfile.obj

Other obj fileMyfile.lst

Myfile.hex


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Examples of Our Program Instructions

MOV C,P1.4

JC LINE1

SETB P1.0

CLR P1.2


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8051 Instruction Set

ACALL: Absolute Call

ADD, ADDC: Add Acc. (With Carry)

AJMP: Absolute Jump

ANL: Bitwise AND

CJNE: Compare & Jump if Not Equal

CLR: Clear Register

CPL: Complement Register

DA: Decimal Adjust

DEC: Decrement Register

DIV: Divide Accumulator by B

DJNZ: Dec. Reg. & Jump if Not Zero

INC: Increment Register

JB: Jump if Bit Set

JBC: Jump if Bit Set and Clear Bit

JC: Jump if Carry Set

JMP: Jump to Address

JNB: Jump if Bit Not Set

JNC: Jump if Carry Not Set

JNZ: Jump if Acc. Not Zero

JZ: Jump if Accumulator Zero

LCALL: Long Call

LJMP: Long Jump

MOV: Move Memory

MOVC: Move Code Memory

MOVX: Move Extended Memory

MUL: Multiply Accumulator by B

NOP: No Operation

ORL: Bitwise OR

POP: Pop Value From Stack

PUSH: Push Value Onto Stack

RET: Return From Subroutine

RETI: Return From Interrupt

RL: Rotate Accumulator Left

RLC: Rotate Acc. Left Through Carry

RR: Rotate Accumulator Right

RRC: Rotate Acc. Right Through Carry

SETB: Set Bit

SJMP: Short Jump

SUBB: Sub. From Acc. With Borrow

SWAP: Swap Accumulator Nibbles

XCH: Exchange Bytes

XCHD: Exchange Digits

XRL: Bitwise Exclusive OR

Undefined: Undefined Instruction

Micro Controller 8051- Soft

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