Microprocessor & Interfacing Lab Experiments

Write an assembly language program to interface LCD and display a string with 8051 Microcontroller.

Aim

Write an assembly language program to interface LCD and display a string with 8051 Microcontroller.

Apparatus:

1. 8051 micro controller kit.
2. PC for connecting the DYNA51 kit.
3. Keil-U-Vision software for compilation of program.
4. LCD PIO CARD for DYNA51.

Theory:Read an analog voltage at the input of ADC given as the knob position using 8051 microcontrollers. An Analog to Digital Converter (ADC) is a very useful feature that converts an analog voltage on a pin to a digital number. The binary counter is initially reset to 0000; the output of integrator reset to 0V and the input to the ramp generator or integrator is switched to the unknown analog input voltage VA. The analog input voltage VA is integrated by the inverting integrator and generates a negative ramp output. The output of comparator is positive and the clock is passed through the AND gate. This results in counting up of the binary counter.

Operating Procedure for ADC Cards:

1. Connect ADC card to 26 pin frc connector of Dyna-51EB.
2. Connect +12V ,-12V and GND supply lines to the ADC card.
3. Connect 16X2 LCD card (J1) to PORT 3 of Dyna-51EB in 4 bit mode.
4. Download the program adc.hex (given in the CD) through flash magic.
5. Apply the analog input at the phono jack on the ADC card.
6. Output will display on LCD card.

Program:

ORG 0000H

LJMP MAIN

ORG 0030H

MAIN: NOP

EN EQU P2.0

RS EQU P2.2

// RW EQU P1.1

DAT EQU P2

LCALL LCD_INT

LCALL CLEAR

LCALL LINE1

MOV DPTR, #MYDATA

LCALL LOOP

LCALL LINE2

MOV DPTR, #MYDAT2

LCALL LOOP

LCALL LINE5

lcall dispH

again: lcall adconver

LCALL LINE3

lcall adisph

lcall adispl

SJMP again

;================================================================== =======

W_NIB: PUSH ACC ;Save A for low nibble

ORL DAT,#0F0h ;Bits 4..7 <- 1

ORL A,#0Fh ;Don't affect bits 0-3

ANL DAT,A ;High nibble to display

SETB EN

CLR EN

POP ACC ;Prepare to send

SWAP A ;...second nibble

ORL DAT,#0F0h ; Bits 4...7 <- 1

ORL A,#0Fh ; Don't affect bits 0...3

ANL DAT,A ;Low nibble to display

SETB EN

CLR EN

RET

;================================================================== =======

LCD_INT: CLR RS

// CLR RW

SETB EN

MOV DAT,#028h

CLR EN

LCALL SDELAY

MOV A,#28h

LCALL COM

MOV A,#0Ch

LCALL COM

MOV A,#06h

LCALL COM

LCALL CLEAR

MOV A,#080H

LCALL COM

RET

;================================================================== =======

DATAW: SETB RS

CLR RW

LCALL W_NIB

LCALL LDELAY

RET

;================================================================== =======

SDELAY: MOV R6,#1

HERE2: MOV R7,#255

HERE: DJNZ R7,HERE

DJNZ R6,HERE2

RET

;================================================================== =======

LDELAY: MOV R6,#1

HER2: MOV R7,#255

HER: DJNZ R7,HER

DJNZ R6,HER2

RET

;================================================================== =======

COM: CLR RS

CLR RW

LCALL W_NIB

LCALL SDELAY

RET

;================================================================== =======

LINE1: MOV A,#80H

LCALL COM

RET

LINE 2: MOV A,#0C0H

LCALL COM

RET

LINE 3: MOV A,#0c9H

LCALL COM

RET

LINE 4: MOV A,#0cah

LCALL COM

RET

LINE 5: MOV A,#0cbh

LCALL COM

RET

;================================================================== =======

LOOP: CLR A

MOVC A,@A+DPTR

JZ GO_B2

LCALL DATAW

LCALL SDELAY

INC DPTR

SJMP LOOP

GO_B2: RET

ADisph:

MOV a,r3

LCALL DATAW

LCALL SDELAY

ret

ADispl:

MOV a,r4

LCALL DATAW

LCALL SDELAY

ret

;================================================================== =======

MYDATA: DB " PIO-ADC-01 ",0

MYDAT2: DB " ADC i/p= ",0

dispH:

MOV a,#48H ;ascii for H

LCALL DATAW

LCALL SDELAY

ret

;================================================================== =======

adconvert:

;----------------------------------------------------------

START EQU P1.0 ; Pin 6 Start

EOC EQU P1.3 ; Pin 7 EOC

OE EQU P1.1 ; Pin 9 Output Enable

ALE EQU P1.2 ; Pin 22 ALE

adata EQU P0 ; Data Lines

;----------------------------------------------------------

; Read one byte of data from adc

; Performs a analog conversion cycle.

; address of channel in register "ADDRESS",

; Returns data in BUFFER

; Destroys A.

MOV adata,#0FFH ; Data lines for input

SETB OE ; Disable output

SETB ALE ; Latch the address

NOP

nop

nop

NOP

SETB START ; Start the conversion

NOP

NOP

NOP

CLR START

NOP

NOP

EOCLOOP:

JNB EOC, EOCLOOP ; Do until EOC high

CLR OE ; Output Enable

MOV a,adata ; Get data in buffer

SETB OE

CLR ALE

Result:The Digital data corresponding to the analog input is shown in the LCD.

Viva Questions:

1. Why 8051 is called 8 bit microcontroller?
2. How much on chip ram is available on 8051
3. What is special Function Registers (SFR)?
4. Which bit of the flag register is set when output overflows to the sign bit?
5. Explain whether Port 0 of 8051 cab be used as input output port?

---

---