A digital signal has the following discrete levels:

  • high level
  • low level

When the signal transitions from high to low or from low to high, a digital edge is created. A digital signal has the following types of edges:

  • Rising—Occurs when the signal transitions from low level to high level.
  • Falling—Occurs with a transition from high level to low level.

    • Triggers configured to act on a rising or falling edge of a digital signal are called edge triggers.

    In the following figure, an edge trigger could be configured to occur either at the place labeled Falling Edge of Signal or at Rising Edge of Signal.