Microchip Technology PIC12F1501, Manual

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2011-2015 Microchip Technology Inc. DS40001609E-page 253
PIC16(L)F1508/9
23.1.5 PWM RESOLUTION
The resolution determines the number of available duty
cycles for a given period. For example, a 10-bit resolu-
tion will result in 1024 discrete duty cycles, whereas an
8-bit resolution will result in 256 discrete duty cycles.
The maximum PWM resolution is ten bits when PR2 is
255. The resolution is a function of the PR2 register
value as shown by
Equation 23-4 .
EQUATION 23-4: PWM RESOLUTION
23.1.6 OPERATION IN SLEEP MODE
In Sleep mode, the TMR2 register will not increment
and the state of the module will not change. If the
PWMx pin is driving a value, it will continue to drive that
value. When the device wakes up, TMR2 will continue
from its previous state.
23.1.7 CHANGES IN SYSTEM CLOCK
FREQUENCY
The PWM frequency is derived from the system clock
frequency (F
OSC
). Any changes in the system clock
frequency will result in changes to the PWM frequency.
Refer to
Section 5.0 “Oscillator Module (With
Fail-Safe Clock Monitor)”
for additional details.
23.1.8 EFFECTS OF RESET
Any Reset will force all ports to Input mode and the
PWM registers to their Reset states.
Note:
If the pulse width value is greater than the
period the assigned PWM pin(s) will
remain unchanged.
Resolution
4 PR2 1 +
   
log
2
 
log
------------------------------------------ bits =
TABLE 23-1: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (F
OSC
= 20 MHz)
PWM Frequency 0.31 kHz 4.88 kHz 19.53 kHz 78.12 kHz 156.3 kHz 208.3 kHz
Timer Prescale 64 4 1 1 1 1
PR2 Value 0xFF 0xFF 0xFF 0x3F 0x1F 0x17
Maximum Resolution (bits) 10 10 10 8 7 6.6
TABLE 23-2: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (F
OSC
= 8 MHz)
PWM Frequency 0.31 kHz 4.90 kHz 19.61 kHz 76.92 kHz 153.85 kHz 200.0 kHz
Timer Prescale 64 4 1 1 1 1
PR2 Value 0x65 0x65 0x65 0x19 0x0C 0x09
Maximum Resolution (bits) 8 8 8 6 5 5