Numerical Bases Used in Programming

Numerical Bases Used in Programming

•

_Hexadecimal

•

_Binary

Hexadecimal Basis

•

Hexadecimal Digits:

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

Decimal, Binary, BCD, & Hexadecimal Numbers

(43)

₁₀

=

(0100 0011)

_BCD

=

( 0010 1011 )

₂

=

Registers

Some 8051 16-bit Register

Some 8-bitt Registers of the 8051

Memory mapping in 8051

• ROM memory map in 8051 family

0000H

0FFFH

0000H

1FFFH 8751

AT89C51 ₈₇₅₂ AT89C52

• RAM memory space allocation in the 8051

00H Register Bank 0

( Stack ) Register Bank 1

Register Bank 2 Register Bank 3

Addressing Modes

•

_Register

•

_Direct

•

_{Register Indirect}

•

_Immediate

•

_Relative

•

_Absolute

•

_Long

Register Addressing Mode

MOV Rn, A ;n=0,..,7

ADD A, Rn

MOV DPL, R6

Direct Addressing Mode

Although the entire of 128 bytes of RAM can be accessed using direct addressing mode, it is most often used to access RAM loc. 30 – 7FH.

MOV R0, 40H MOV 56H, A

MOV A, 4 ; ≡ MOV A, R4

MOV 6, 2 ; copy R2 to R6

Register Indirect Addressing Mode

• _{In this mode, register is used as a pointer to the}

data.

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 is sources or target in MOV, ADD and SUBB

Immediate Addressing Mode

MOV A,#65H

MOV R6,#65H

MOV DPTR,#2343H

Relative, Absolute, & Long Addressing

Used only with jump and call instructions:

SJMP

ACALL,AJMP

Indexed Addressing Mode

• This mode is widely used in accessing data

elements of look-up table entries located in the program (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 the

program (code ) space ROM of the 8051, it uses the instruction MOVC instead of MOV. The

Some Simple Instructions

MOV dest,source ; dest = source

MOV A,#72H ;A=72H

MOV R4,#62H ;R4=62H

MOV B,0F9H ;B=the content of F9’th byte of RAM

MOV DPTR,#7634H MOV DPL,#34H MOV DPH,#76H

MOV P1,A ;mov A to port 1

Note 1:

MOV A,#72H ≠ MOV A,72H

After instruction “MOV A,72H ” the content of 72’th byte of RAM will replace in Accumulator.

Note 2:

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

SUBB

A, Source

;A=A-SOURCE-C

MUL & DIV

• MUL AB ;B|A = A*B

MOV 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,#25

MOV B,#10

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

DEC

byte

;byte=byte-1

INC

byte

;byte=byte+1

INC

R7

DEC

A

RR – RL – RRC – RLC A

EXAMPLE:

RR A

RR:

RRC:

RL:

RLC:

C

ANL - ORL – XRL

Bitwise Logical Operations: AND, OR, XOR

EXAMPLE:

MOV R5,#89H ANL R5,#08H

CPL A ;1’s complement

Example:

MOV A,#55H ;A=01010101 B

L01: CPL A

MOV P1,A

ACALL DELAY

Stack in the 8051

• The register used to

access the stack is called

SP (stack pointer) register.

• The stack pointer in the 8051 is only 8 bits wide, which means that it can take value 00 to FFH. When 8051 powered up, the SP register contains value 07.

00H Register Bank 0 ( Stack ) Register

Bank 1 Register Bank 2 Register Bank 3 Bit-Addressable RAM

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

DJNZ:

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

Solution:

MOV A,#0 MOV R2,#10 AGAIN: ADD A,#03

LJMP(long jump)

LJMP is an unconditional jump. It is a 3-byte instruction. It allows a jump to any memory location from 0000 to

FFFFH.

AJMP(absolute jump)

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

SJMP(short jump)

CALL Instructions

Another 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 target

address of the subroutine must be within 2K

Example:

Write a program to copy a block of 10 bytes from RAM location 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 R0

INC R1

. 100's 10's 1's

. 1 5 6

+ 2 4 8

= 4 0 4

Decimal Addition

156 + 248

16 Bit Addition

1A44 + 22DB

. 256's 16’s 1's

. 1 A 4 4

+ 2 2 D B

= 3 D 1 F

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.

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.

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 process

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

;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

Timer & Port Operations

• Example:

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

MOV TMOD,#02H ;8-bit auto-reload mode MOV 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

Interrupts

1. Enabling and Disabling Interrupts

2. Interrupt Priority

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.

Interrupt Vectors

Interrupt Vector Address

System Reset 0000H External 0 0003H

Timer 0 000BH

External 1 0013H

Timer 1 001BH

Serial Port 0023H

Writing the ISR

Example:

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

. .

Structure of Assembly language and

Running an 8051 program

EDITOR PROGRAM

ASSEMBLER PROGRAM

LINKER PROGRAM

OH PROGRAM

Myfile.asm

Myfile.obj

Other obj file Myfile.lst

Examples of Our Program Instructions

•

MOV C,P1.4

JC LINE1

•

_{SETB P1.0}

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