PWM function of PIC16F877A microcontroller

 To configure the CCP module for PWM mode, follow these steps:
1. Write to the PR2 register to program the PWM period.
2. Write to the DCxB9:DCxB0 bits to program the PWM duty cycle.
3. Clear the appropriate TRIS bit to make the CCPx pin an output.
4. Write to T2CON to program the TMR2 prescaler and enable Timer2.
5. Configure the CCP module for PWM mode.

program:

#include
#define uint unsigned int
#define uchar unsigned char
__CONFIG(0x3B31);

void initPWM();
void Delay1ms(uint time);

/******************************************
***Main function: PWM initialization, PWM duty cycle periodic change
*******************************************/
void main()
{
 uchar i;
 initPWM();
 while(1)
 {
  for(i=0;i<256;i++)
  {
   CCPR1L = i;
   TMR2ON = 1;
   Delay1ms(100);
   TMR2ON = 0;   
  }
 } 
 
}

/******************************************************************
***Function: PWM initialization, set PWM period;
PWM period = [(PR2)+1]*4*TOSC*(TMR2 pre-scaling ratio)
       = (255+1)*4*(1/4000000)*16 s = 4.096 ms

PWM duty cycle = (DCxB9:DCxB0)*Tosc*(TMR2 prescaler ratio)
  = 1024*(1/4000000)*16 s = 4.096 ms

Note: If the PWM duty cycle value is greater than the PWM period, the CCPx pin will
      not be cleared and the duty cycle will reach 100%;

*********************************************************************/
void initPWM()
{
 INTCON = 0x00; //Disable general interrupt and external interrupt
 PR2 = 0xff; //Write to PR2 register to set PWM period, PWM period = [(PR2)+1]*4*TOSC*(TMR2 prescaler)
 CCP1CON = 0x3C; //Set the lower 2 bits of PWM duty cycle to 11, set to PWM mode
 CCPR1L = 0x00; //Set the higher 8 bits of PWM duty cycle
 TRISC = 0xfb; //Set CCP1 port to output
 T2CON = 0x02; //Set TMR2 prescaler to 16; 
}

void Delay1ms(uint time)
{
 uint i,j;
 for(i=time;i>0;i--)
  for(j=110;j>0;j--);
}