The mode of operation determines the behavior of the Timer/Counter and the Output Compare pins. It is defined by the combination of the Waveform Generation mode bits and Compare Output mode (TCCR0A.WGM0[2:0]) bits in the Timer/Counter control Registers A and B (TCCR0A.COM0x[1:0]). The Compare Output mode bits do not affect the counting sequence, while the Waveform Generation mode bits do. The COM0x[1:0] bits control whether the PWM output generated should be inverted or not (inverted or non-inverted PWM). For non-PWM modes the COM0x[1:0] bits control whether the output should be set, cleared, or toggled at a compare match (See previous section Compare Match Output Unit).
For detailed timing information refer to the following section Timer/Counter Timing Diagrams.