Sequential Logic

A sequential circuit has the key addition of state, or memory: elements that remember the past.

The circuit below detects a particular sequence of input values. Note that when top input is 1 and bottom input is 0, the output can be 0 or 1 depending on the current state (values in D flip-flops).

In fact, the output is set to 1, if the top input stays at 1 while the bottom input goes from 0 to 1, then to 0 again.

You can open the sequential.circ file in Logisim to examine this circuit.