PIC16F882/883/884/886/887
11.5.3
PWM RESOLUTION
EQUATION 11-4: 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.
log[4(PR2 + 1)]
Resolution = ----------------------------------------- bits
log(2)
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 11-4.
Note:
If the pulse width value is greater than the
period the assigned PWM pin(s) will
remain unchanged.
TABLE 11-3: 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)
PR2 Value
16
0xFF
10
4
1
1
0x3F
8
1
0x1F
7
1
0xFF
10
0xFF
10
0x17
6.6
Maximum Resolution (bits)
TABLE 11-4: 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)
PR2 Value
16
0x65
8
4
0x65
8
1
0x65
8
1
0x19
6
1
0x0C
5
1
0x09
5
Maximum Resolution (bits)
DS41291D-page 130
Preliminary
© 2007 Microchip Technology Inc.
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