represents special cases when generating a
PWM waveform output in the fast PWM mode. If the OCR0 is set equal to BOTTOM, the
output will be a narrow spike for each MAX+1 timer clock cycle. Setting the OCR0 equal
to MAX will result in a constantly high or low output (depending on the polarity of the output
set by the COM01:0 bits.)
A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved
by setting OC0 to toggle its logical level on each compare match (COM01:0 = 1). The
waveform generated will have a maximum frequency of fOC0 = fclk_I/O/2 when OCR0 is
set to zero. This feature is similar to the OC0 toggle in CTC mode, except the double
buffer feature of the output compare unit is enabled in the fast PWM mode."