23.5 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 23-4. PWM Resolution

Re s o l u t i o n = \frac{\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 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
T2PR 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
T2PR Value	0x65	0x65	0x65	0x19	0x0C	0x09
Maximum Resolution (bits)	8	8	8	6	5	5