Datasheet

PICkit™ 3 Debug Express

FIGURE 3-60: SIMPLIFIED PWM BLOCK DIAGRAM

Now that the frequency has been determined, it is necessary to set up the CCP1

module for PWM using the CCP1CON register. Bits CCP1Mx determine the module

mode; there is only one value to select for PWM, CCP1Mx = 0b11xx where the ‘x’ bits

are “don’t care”, so 0b1100 will work. The two DC1Bx bits in CCP1CON are the 2 Least

Significant bits of the 10-bit PWM duty cycle value. The 8 Most Significant of the 10 bits

are written to CCPR1L.

The duty cycle value is determined by the duty cycle percentage (DC%) times the 10-bit

time base (PR2 * 4). DCValue = DC% * (PR2 * 4). For example, to get a duty cycle of

50%, the value would be 50% * (250 * 4) = 500. 500 decimal is 0x1F4 hex or 0b01 1111

0100 binary. The 8 Most Significant bits, 0b01 1111 01 or 0x7D, are written to CCPR1L,

and the 2 LSbs are written to the DC1B1 and DC1B0 bits in CCP1CON.