AT89C52 and Multiplexed Display in C using Keil

Programming for multiplexed display in C is straight forward. MCS-51 controller just turn on each digit around 5ms. An important parameter is timing delay created by controller. A timer is need to create a precise timing for controller. 

However we can use a delay time created by instruction in C loop. It’s not more precise but we can predict this timing delay in both simulator or physical hardware.

 In this typical example, AT89C52 drives a two-digit multiplexed display. The display is common cathode type. P2 drives display’s segments while P3 drives display’s digits.

In C program we use “for loop” to create timing delay by estimation.

#include <REG52.h>

sbit en1=P3^0;

sbit en2=P3^1;

void delay(unsigned int cnt);

void display(unsigned char d1,unsigned char d2);

// common anode

//unsigned char SSD[16]={0xC0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90,0x88,0x83,0xC6,0xA1,0x86,0x8E};

//common cathode

unsigned char SSD[16]={0x3F,0x06,0x5B,0x4F,0x66,0x6D,0x7D,0x07,0x7F,0x6F,0x77,0x7C,0x39,0x5E,0x79,0x71};

unsigned char cnt=0;

void main(){

P2=0x00;

P3=0x00;

while(1) display(9,10);

}

void delay(unsigned int time){

int opt;

for(opt=0;opt<time;opt++);

}

void display(unsigned char d1,unsigned char d2){

P2=SSD[d1];

en1=1;

delay(3000);

en1=0;

P2=SSD[d2];

en2=1;

delay(3000);

en2=0;

}

Click here to download this example program package.