Microchip Technology MA160014 Data Sheet
PIC18(L)F2X/4XK22
DS41412F-page 188
2010-2012 Microchip Technology Inc.
14.3.6
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.
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 ten bits when PRx is
255. The resolution is a function of the PRx register
value as shown by
255. The resolution is a function of the PRx register
value as shown by
.
EQUATION 14-4:
PWM RESOLUTION
14.3.7
OPERATION IN SLEEP MODE
In Sleep mode, the TMRx 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, TMRx will continue from its
previous state.
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, TMRx will continue from its
previous state.
14.3.8
CHANGES IN SYSTEM CLOCK
FREQUENCY
FREQUENCY
The PWM frequency is derived from the system clock
frequency. Any changes in the system clock frequency
will result in changes to the PWM frequency. See
frequency. Any changes in the system clock frequency
will result in changes to the PWM frequency. See
14.3.9
EFFECTS OF RESET
Any Reset will force all ports to Input mode and the
CCP registers to their Reset states.
CCP registers to their Reset states.
Note:
If the pulse width value is greater than the
period the assigned PWM pin(s) will
remain unchanged.
period the assigned PWM pin(s) will
remain unchanged.
Resolution
4 PRx
1
+
log
2
log
------------------------------------------ bits
=
TABLE 14-7:
EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (F
OSC
= 32 MHz)
PWM Frequency
1.95 kHz
7.81 kHz
31.25 kHz
125 kHz
250 kHz
333.3 kHz
Timer Prescale (1, 4, 16)
16
4
1
1
1
1
PRx Value
0xFF
0xFF
0xFF
0x3F
0x1F
0x17
Maximum Resolution (bits)
10
10
10
8
7
6.6
TABLE 14-8:
EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (F
OSC
= 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
PRx Value
0xFF
0xFF
0xFF
0x3F
0x1F
0x17
Maximum Resolution (bits)
10
10
10
8
7
6.6
TABLE 14-9:
EXAMPLE PWM FREQUENCIES AND RESOLUTIONS (F
OSC
= 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
PRx Value
0x65
0x65
0x65
0x19
0x0C
0x09
Maximum Resolution (bits)
8
8
8
6
5
5