Counter
Counter is a sequential logic circuit which has a clock input signal and a group of output signals that represent an integer “counts” value. Upon each qualified clock edge, the circuit will increment the counts. When the counts have reached the end of the counting sequence , the next clock will cause the counts to overflow or underflow and the counting sequence will start over. Internally, counters use flip-flops to represent the current counts and to retain the counts between clocks.
