why timer is required in this?

[ashish]

Example-2: write a program to make 8 to 1 multiplexer with enable signal

#include<reg51.h>

sbit D0 = P0^0;                     // set P0.0-P0.7 (D0-D7) as input pins of mux
sbit D1 = P0^1;
sbit D2 = P0^2;
sbit D3 = P0^3;
sbit D4 = P0^4;
sbit D5 = P0^5;
sbit D6 = P0^6;
sbit D7 = P0^7;
sbit S0 = P1^0;                 // set P1.0-P1.2(S0-S2) as select pins of mux
sbit S1 = P1^1;
sbit S2 = P1^2;
sbit EN = P1^7;                // set P1.7 as enable pin
sbit pin = P3^5;               // set P3.5 as output 

main()
{
         P3=0x00;P0=0xFF;      // clear op and set all ips
        TMOD = 0x01;              // set timer 0 for 16 bit timer
 next:TL0 = 0xAF;                 // load count 
        TH0 = 0x3C; 
        while(EN==1){}           // wait till enable pin becomes 0
   if((S0==0)&&(S1==0)&&(S2==0)) pin = D0;                  // if select inputs are 000 op is first ip
   else if((S0==1)&&(S1==0)&&(S2==0)) pin = D1;           // if select inputs are 001 op is second ip
   else if((S0==0)&&(S1==1)&&(S2==0)) pin = D2;           // same as above
   else if((S0==1)&&(S1==1)&&(S2==0)) pin = D3;
   else if((S0==0)&&(S1==0)&&(S2==1)) pin = D4;
   else if((S0==1)&&(S1==0)&&(S2==1)) pin = D5;
   else if((S0==0)&&(S1==1)&&(S2==1)) pin = D6;
   else if((S0==1)&&(S1==1)&&(S2==1)) pin = D7;   
   else pin = 0;                                                                 // by default op is cleared
   TR0 = 1;                                                                      // start timer 0 
   while(TF0==0){}                                                          // wait until overflow means 50ms
   TR0 = 0;                                                                      // stop timer 
   goto next;                                                                    // go for next input 
}  

[AJISH ALFRED]

Hi,

Here the timer is used to generate a precise 50 milli second delay before taking the next input.

[Ashutosh Bhatt]

you can remove this delay also. 

the program will work

[Author]

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