Mikrocontroller wird nach dem Programmieren nicht mehr zum erneuten programmieren erkannt

/*

 * Project name:

     Funkuhr

 * Copyright:

     (c) Peter Schumacher 2013.

 * Description:

     Funkuhr

 * Test configuration:

     MCU:             PIC18F1320-I/P

                      http://ww1.microchip.com/downloads/en/devicedoc/39605f.pdf

     dev.board:       EasyPIC v7

                      http://www.mikroe.com/eng/products/view/757/easypic-v7-development-system/

     internal Oscillator: 125 kHz

     external Oscillator: 32,768 kHz external Crystal

     Ext. Modules:    DCF-77-Receiver

                      http://ele.pgbesa.net/DCF77.pdf

     SW:              mikroC PRO for PIC

                      http://www.mikroe.com/eng/products/view/7/mikroc-pro-for-pic/

 */

// LCD module connections

sbit LCD_RS at LATA0_bit;

sbit LCD_EN at LATA1_bit;

sbit LCD_D4 at LATA2_bit;

sbit LCD_D5 at LATA3_bit;

sbit LCD_D6 at LATA4_bit;

sbit LCD_D7 at LATB5_bit;

sbit LCD_RS_Direction at TRISA0_bit;

sbit LCD_EN_Direction at TRISA1_bit;

sbit LCD_D4_Direction at TRISA2_bit;

sbit LCD_D5_Direction at TRISA3_bit;

sbit LCD_D6_Direction at TRISA4_bit;

sbit LCD_D7_Direction at TRISB5_bit;

#define Empfaenger LATA.F6

#define Signal LATA.F7

char s = 0;                                   //Sekunde

char m = 0;                                   //Minute

char h = 0;                                   //Stunde

char d = 0;                                   //Tag

char wd = 1;                                  //Wochentag (Mo.-So.)

char mt = 0;                                  //Monat

//Einzelne Ziffern für Ausgabestring

char h1 = 0;

char h2 = 0;

char m1 = 0;

char m2 = 0;

char s1 = 0;

char s2 = 0;

char txt[9];                                  //Uhrzeit-String

//oder:

//char *txt = "00:00:00";

char Freigabe = 0;                            //Funksignal wird empfangen

void interrupt() {

  if(Freigabe == 0){

    Empfaenger = 1;

    if(Signal){

      LATB.F1 = 1;                            //Pin 9

    }

    else{

      LATB.F1 = 0;                            //Pin 9

    }

    Freigabe = 0;

  }

  s++;

  if(s == 60){

    s = 0;

    m++;

  }

  if(m == 60){

    m = 0;

    h++;

  }

  if(h == 24){

    h = 0;

    wd++;

  }

  TMR1IF_bit = 0;

  INT0IF_bit = 0;                             //Reset von: INT0 External Interrupt Flag bit

}

void main() {

//OSCCON REGISTER

  IDLEN_bit = 0;                              //Run Mode enabled

  IRCF2_bit = 0;                              //internen Oszillator im OSCCON-Register auf 125 kHz setzen

  IRCF1_bit = 0;

  IRCF0_bit = 1;

//Port A konfigurieren

  TRISA = 0;                                  //Port A als Ausgänge definieren

  TRISA.F7 = 1;                               //Pin 4 von Port A als Eingang definieren

  PORTA = 0;                                  //Anfangswert von Port A festlegen

//Port B konfigurieren

  TRISB = 0;                                  //Port B als Ausgänge definieren

  TRISB.F0 = 1;                               // Pin 0 von Port B als Eingang definieren

  PORTB = 0;                                  //Anfangswert von Port B festlegen

//LCD einrichten

  Lcd_Init();

  Lcd_Cmd(_LCD_CLEAR);

  Lcd_Cmd(_LCD_CURSOR_OFF);

//INTCON REGISTER

  GIE_bit = 1;                                //Enables all unmasked interrupts

  PEIE_bit = 1;                               //Enables all unmasked peripheral interrupts

  INT0IE_bit = 1;                             //INT0 External Interrupt Enable bit (S1-Button at RB0)

  INT0IF_bit = 0;                             //Reset von: INT0 External Interrupt Flag bit

//T1CON REGISTER

  TMR1ON_bit = 1;                              //Enables Timer1

  TMR1CS_bit = 1;                              //External clock from pin RB6/PGC/T1OSO/T13CKI/P1C/KBI2 (on the rising edge)

  T1SYNC_bit = 1;                              //Do not synchronize external clock input

  T1OSCEN_bit = 1;                             //Timer1 Oscillator Enable bit

  TMR1H = 0x80;                                //Timer1 ist ein 16bit Timer. Hier wrird das höhere Byte "vorgeladen" ("preload"), damit ein Interrupt genau nach jeder Sekunde kommt.

  do{

    LATB.F4 = 1;

    //Uhrzeit wird in String umgewandelt

    h1 = (h / 10) % 10;

    h2 = (h     ) % 10;

    m1 = (m / 10) % 10;

    m2 = (m     ) % 10;

    s1 = (s / 10) % 10;

    s2 = (s     ) % 10;

    txt[0] = '0' + h1;

    txt[1] = '0' + h2;

    txt[2] = ':';

    txt[3] = '0' + m1;

    txt[4] = '0' + m2;

    txt[5] = ':';

    txt[6] = '0' + s1;

    txt[7] = '0' + s2;

    txt[8] = '\0';                            //Strings: http://www.mikrocontroller.net/articles/String-Verarbeitung_in_C

    Lcd_Out(1, 1, txt);

    switch(wd){

      case(1): {Lcd_Out(1,15,"Mo"); break;}

      case(2): {Lcd_Out(1,15,"Di"); break;}

      case(3): {Lcd_Out(1,15,"Mi"); break;}

      case(4): {Lcd_Out(1,15,"Do"); break;}

      case(5): {Lcd_Out(1,15,"Fr"); break;}

      case(6): {Lcd_Out(1,15,"Sa"); break;}

      case(7): {Lcd_Out(1,15,"So"); break;}

      default: break;

    }

    Lcd_Cmd(_LCD_RETURN_HOME);

  }while(1);

}