Frequência com TIMER0 no PIC 16F877A

Código feito no CCS C Compiler

#include <16F877A.h>

#device adc = 8

#FUSES NOWDT, HS, NOPUT, NOPROTECT, NODEBUG, BROWNOUT, NOLVP, NOCPD, NOWRT, NOWRT

#use delay(clock = 20MHz)

unsigned int16 cont1 = 0, cont2 = 0, cont3 = 0;

/*Contagem  frequencia de entrada

   PARA 220 Hz

   PARA 95 Hz

   PARA 82 Hz 

*/

// 274 Hz ---> 36 ---> 3.65ms

#int_TIMER0

void TIMER0_isr(void){

   if(++cont1 >= 44)  { cont1 = 0; output_toggle(pin_B0) ; } // [274 * 36] / 220) = 44

   if(++cont2 >= 103) {cont2 = 0;output_toggle(pin_B1); } //   [274 * 36] / 95 = 103

   if(++cont3 >= 120) {cont3 = 0; output_toggle(pin_B2); } //  [274 * 36] / 82 = 120

}

void main(){

   setup_adc_ports(NO_ANALOGS);

   setup_adc(ADC_OFF);

   setup_psp(PSP_DISABLED);

   setup_spi(SPI_SS_DISABLED);

   setup_timer_0(RTCC_INTERNAL | RTCC_DIV_1); // overflow 51,2 us

   setup_timer_1(T1_DISABLED);

   setup_timer_2(T2_DISABLED,0,1);

   setup_comparator(NC_NC_NC_NC);

   setup_vref(FALSE);

   enable_interrupts(INT_TIMER0);

   enable_interrupts(GLOBAL);

   //disable_interrupts(GLOBAL);

   

   while(true);

}

Saída gerada no software Proteus 7.9