49.6.2.5.5 Single-Slope PWM Operation

For single-slope PWM generation, the period time (T) is controlled by Top value, and CCx controls the duty cycle of the generated waveform output. When up-counting, the WO[x] is set at start or compare match between the COUNT and TOP values, and cleared on compare match between COUNT and CCx register values. When down-counting, the WO[x] is cleared at start or compare match between the COUNT and ZERO values, and set on compare match between COUNT and CCx register values.

The following equation calculates the exact resolution for a single-slope PWM (R_{PWM_SS}) waveform: 

R_{PWM_SS} = \frac{log(TOP+1)}{log(2)}

The PWM frequency depends on the Period register value (PER) and the peripheral clock frequency (f_{GCLK_TCCx}), and can be calculated by the following equation:

f_{PWM_SS} = \frac{f_{GCLK_TCCx}}{N(TOP+1)}

Where N represents the prescaler divider used (1, 2, 4, 8, 16, 64, 256, 1024).