22.4.6 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.

The maximum PWM resolution is ten bits when T2PR is 255. The resolution is a function of the T2PR register value as shown below.

Equation 22-4. PWM Resolution
Re s o l u t i o n = log [ 4 ( T 2 P R + 1 ) ] log ⁡ ( 2 ) b i t s
Important: If the pulse-width value is greater than the period, the assigned PWM pin(s) will remain unchanged.
Table 22-3. 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 16 4 1 1 1 1
T2PR Value 0xFF 0xFF 0xFF 0x3F 0x1F 0x17
Maximum Resolution (bits) 10 10 10 8 7 6.6
Table 22-4. 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 16 4 1 1 1 1
T2PR Value 0x65 0x65 0x65 0x19 0x0C 0x09
Maximum Resolution (bits) 8 8 8 6 5 5