How Skew Affects Differential Signals

An eye diagram of a differential signal in which there is skew between the two contributing channel signals can result in three "logic" levels as shown in the following pictures. After the two signals have been deskewed, a traditional eye diagram will be displayed that shows two logic levels.

The following drawings show the logic levels before and after an Auto Deskew on two skewed input signals. The differential signal is Channel 1 minus Channel 2. Notice in the top picture that there are three "logic" levels: -1V, 0V, and +1V.