Datasheet
2010-2011 Microchip Technology Inc. DS41418B-page 137
PIC16(L)F707
17.3.4 PWM RESOLUTION
The resolution determines the number of available duty
cycles for a given period. For example, a 10-bit resolution
will result in 1024 discrete duty cycles, whereas an 8-bit
resolution will result in 256 discrete duty cycles.
The maximum PWM resolution is 10 bits when PR2 is
255. The resolution is a function of the PR2 register
value as shown by Equation 17-4.
EQUATION 17-4: PWM RESOLUTION
17.3.5 OPERATION IN SLEEP MODE
In Sleep mode, the TMR2 register will not increment
and the state of the module will not change. If the CCPx
pin is driving a value, it will continue to drive that value.
When the device wakes up, TMR2 will continue from its
previous state.
17.3.6 CHANGES IN SYSTEM CLOCK
FREQUENCY
The PWM frequency is derived from the system clock
frequency (F
OSC). Any changes in the system clock fre-
quency will result in changes to the PWM frequency.
Refer to Section 7.0 “Oscillator Module” for
additional details.
17.3.7 EFFECTS OF RESET
Any Reset will force all ports to Input mode and the
CCP registers to their Reset states.
17.3.8 SETUP FOR PWM OPERATION
The following steps should be taken when configuring
the CCP module for PWM operation:
1. Disable the PWM pin (CCPx) output driver(s) by
setting the associated TRIS bit(s).
2. Load the PR2 register with the PWM period value.
3. Configure the CCP module for the PWM mode
by loading the CCPxCON register with the
appropriate values.
4. Load the CCPRxL register and the DCxBx bits of
the CCPxCON register, with the PWM duty cycle
value.
5. Configure and start Timer2:
• Clear the TMR2IF interrupt flag bit of the
PIR1 register. See Note below.
• Configure the T2CKPS bits of the T2CON
register with the Timer2 prescale value.
• Enable Timer2 by setting the TMR2ON bit of
the T2CON register.
Note: If the pulse width value is greater than the
period the assigned PWM pin(s) will
remain unchanged.
Resolution
4PR2 1+log
2log
------------------------------------------ bits=
TABLE 17-5: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 20 MHz)
PWM Frequency 1.22 kHz 4.88 kHz 19.53 kHz 78.12 kHz 156.3 kHz 208.3 kHz
Timer Prescale (1, 4, 16) 16 4 1 1 1 1
PR2 Value 0xFF 0xFF 0xFF 0x3F 0x1F 0x17
Maximum Resolution (bits) 10 10 10 8 7 6.6
TABLE 17-6: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (FOSC = 8 MHz)
PWM Frequency 1.22 kHz 4.90 kHz 19.61 kHz 76.92 kHz 153.85 kHz 200.0 kHz
Timer Prescale (1, 4, 16) 16 4 1 1 1 1
PR2 Value 0x65 0x65 0x65 0x19 0x0C 0x09
Maximum Resolution (bits) 8 8 8 6 5 5