PIC16F88 _ FREQ TMR2 switch

void interrupt() {
  if (TMR2IF_bit) {
    TMR2IF_bit = 0;           // mazu FLAG
   // TMR2 = 0;                 // resetuju TMR2    filip rika ze nemusim
    PORTB = ~PORTB;           // prepinam PORTB
  }
}

void main() {
     ANSEL = 0;       //vypneme
     CMCON = 7;       //sracky
     TRISB = 0;       //B vystup
     TRISA = 255;     //vstup
     T2CON = 39;      //nastaveni tmr2 - zapnutej, postsc:4 / presc: 16
     INTCON = 192;    //GLOBAL INTERRUPT ENABLED + PEIE -> preruseni od perif.
     while(1){
     switch(PORTA & 0x07){
                   case 0:
                        PR2 = 156;
                        break;
                   case 1:
                        PR2 = 78;
                        break;
                   case 2:
                        PR2 = 39;
                        break;
                   case 3:
                        PR2 = 20;
                        break;
                   case 4:
                        PR2 = 10;
                        break;
                   case 5:
                        PR2 = 5;
                        break;
                   case 6:
                        PR2 = 2;
                        break;
                   case 7:
                        PR2 = 1;
                        break;
                   default:
                        PR2 = 156;
     }    }
}