A PIC16F628A has an in-built Capture/Compare/PWM (CCP) module for which the I/O pin is served by RB.3 (Pin No. 9). In this experiment we are going to use the CCP as a PWM to control the power to a LED. PWM stands for the Pulse Width Modulation where the width of a digital waveform is varied to control the power delivered to a load. The underlying principle in the whole process is that the average power delivered is directly proportional to the modulation duty cycle. The term duty cycle describes the proportion of on time to the regular interval or period of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.
Image Source: http://www.micromouseinfo.com/introduction/images/intro_hardware/PWMod.gifThe mikroC has an in-built library functions for PWM hardware module. Click here for details.