Waveform Generation Modes

The TCD provides four different waveform generation modes. The waveform generation modes determine how the counter is counting during a TCD cycle, and when the compare values are matching. A TCD cycle is split into these states:

In a standard configuration all states are present in the order they are listed and they are non-overlapping. The compare values Compare A Set (TCD.CMPASET), Compare A Clear (TCD.CMPACLR), Compare B Set (TCD.CMPBSET) and Compare B Clear (TCD.CMPBCLR) defines when each of the states are ending and the next is beginning. There are four different ways to go through a TCD cycle. The different ways are called Waveform Generation Modes. They are controlled by the Waveform Generation Mode bits (WGMODE) in the Control A register (TCD.CTRLA). The waveform generation modes are:

The name indicates how the counter is operating during one TCDcycle.