Implementing a 4-bit counter using an 8051 and Interfacing it a 7-segment display

Introduction

In this lab, you will learn how to write a simple C program for 80X51 micro-controller, compile it using C51 compiler, and burn it unto an 8051 chip. The program will be used to control a simple 4-bit up-down counter, capable of counting from 0 to F. At each step the count should be displayed in hexadecimal on the 7-segment display. You will control the the counter using a DIP switch which is also interfaced to the 8051 chip.

For the seven segment display we will be using the LSD5061-11 chip. Each of the segments of the display is connected to a pin on the 8051 (the schematic shows how to do this). In order to light up a segment on the the pin must be set to 0V. To turn a segment off the corresponding pin must be set to 5V. This is simply done by setting the pins on the 8051 to '1' or '0'. See the figure below to determine which segment corresponds to which pin. This will be important when you fill in you lookup table.

Segment number	LSD5061-11 Pin number	8051 pin number
s1	pin 1	P2.0
s2	pin 2	P2.1
s3	pin 4	P2.2
s4	pin 6	P2.3
s5	pin 7	P2.4
s6	pin 9	P2.5
s7	pin 10	P2.6

                          

Assignment

In this lab :

• You will design a 4-bit Up-Down counter using the C programming language for the 8051 micro-controller and display the count on an LCD.



• You will then burn your program on the 8051.



• The 4 bit counter has the following functionality:
  • The counter has the following input pins :
    1. Reset : when high resets the counter dataout to ``0000''
    2. Updown : decides whether the counter counts up or down.
    3. Load : makes the counter count from the 4 bit input Datain
    4. Datain : which is a 4 bit input count
  • The counter has a 4 bit Dataout to reflect the count.
  • The count has to be sent to the 7-segment display and shown in hexadecimal format.

Apparatus Required

1. 4.7k resistors(7)
2. 330 resistors(2)
3. DIP switch
4. 7-segment display
5. 5V power supply
6. 8051 chip
7. 12MHz crystal (clock)

Schematic

Program

#pragma SMALL DB
#include 

/* P0, P1, P2 and P3 are predefined port names and are bit addressable */

sbit reset = P0^4; /* bit 4 of Port 0 */
sbit up_down = P0^5;
sbit load = P0^6;

void SetDisplay(unsigned char value){
    
    unsigned char LookupTable[17] = { 0xC0, .... };   /* fill in the */
                                                      /* rest of the lookup table */	

    if( value >= 0 && value < 16 ) {
	/* assign port2 the appropriate */ 
	/* value in the lookup table */
    }
    else {
        /* assign port 2 the error */
        /* condition from the lookup table */
    }
}


/* Delay function */
void delay() {
    
    int i, j;
    
    for(i=0; i<1000; i++)
	for(j=0; j<100; j++)
	    i = i + 0;
}


void main(void){
    unsigned char count = 0;
    
    while(1) {
	if(reset == 1){
	    /* set count to 0 */
            /* display 0 on 7-seg */
	    delay();
	}
	else if(load == 1){
	    /* set count to the value read from port 0 */
	    /* display the value read on the 7-seg */
	    delay();
	}
	else{
	    if(up_down==1){
		/* increment count, keep it within bounds */
		/* display the value on the 7-seg */
		delay();
	    }
	    else{
		/* decrement count, keep it within bounds */
		/* display the value on the 7-seg */
		delay();
	    }
	}
    }
}

Procedure

Hardware

1. Wire up the circuit as shown in the schematic.
2. Pinouts are also available:
   1. 8051
   2. 7-segment display