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PIN_B5 problem

 
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ariza



Joined: 16 Mar 2005
Posts: 13

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PIN_B5 problem
PostPosted: Sat Jun 11, 2005 2:12 pm     Reply with quote
Hi
In my project I have an interface between 74ls90 (counter) and 18f452.
I obtain a value with using 74ls90 nad then using 18f452's ext interrupt routine to take the value of counter. From B4-B7 I take the 4 bit value of counter, I take this information and do different jobs that changes with the value of B4--B7 value.
My problem is when the counter value is 2,3,6,7 (where the B5 pin is high) my program doesn't work. it does not do anything. here is my code
Code:

#include <18F452.h>
#device adc=8
#use delay(clock=10000000)
#fuses NOWDT,WDT128,HS, BORV20

#byte pa   =0xF80   
#byte pb   =0xF81   
#byte pc   =0xF82   
#byte pd   =0xF83

int8 n=0;
int8 count=0;
int8 a,b=1;
#bit t4      =pb.7
#bit t3      =pb.6
#bit t2      =pb.5
#bit t1      =pb.4

void init(void)
 {
   SET_TRIS_B(0xf7);
   SET_TRIS_C(0x00);
   SET_TRIS_D(0x00);
   
 }
#int_EXT
EXT_isr()
{

    pc=count;
    delay_ms(170);
    pc=0;

 if(b==1)
 {
    if((t4==0)&&(t3==0))
          {
           if((t2==0)&&(t1==1))
            { n=1;pc=n;
            delay_ms(170);
            start();
              break;
            }
           if((t2==1)&&(t1==0))
            { n=2;pc=n;
            delay_ms(170);
            start();
              break;
            }
           if((t2==1)&&(t1==1))
            { n=3;pc=n;
            delay_ms(170);
            start();
              break;
            }
          }
    if((t4==0)&&(t3==1))
          {
           if((t2==0)&&(t1==0))
            {  n=4;pc=n;
            delay_ms(170);
            change();
               break;
            }
           if((t2==0)&&(t1==1))
            {  n=5;pc=n;
            delay_ms(170);
             change();
               break;
            }
           if((t2==1)&&(t1==0))
            {  n=6; pc=n;
            delay_ms(170);
             change();
               break;
            }
           if((t2==1)&&(t1==1))
            {  n=7;pc=n;
            delay_ms(170);
             change();
               break;
            }
          }
    else
     break;
  }
     
}


Thanks for Advice

Best Regards
Ariza Razz
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Sat Jun 11, 2005 3:02 pm     Reply with quote
Pin B5 is used for Low Voltage Programming, which is enabled by default
on new chips. If pin B5 is set at a logic-high level, the PIC will go into
LVP programming mode. Solution: Add the NOLVP parameter to
your #fuses statement. Example:

#fuses NOWDT, WDT128, HS, BORV20, NOLVP
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