Counter Counters are sequential circuits which "count" through a specific statesequence. The sequence of states: may follow the binary number sequence (⇒ Binary counter) or anyother sequence of states Categories of counters: Ripple counters: The flip-flop output transition serves as a source for triggering otherflip-flops.⇒ The C input of some or all flip-flops are triggered not by thecommon clock pulses. (not synchronous) Synchronous counters: The C inputs of all flip-flops receive the common clock.