shift counter

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shift counter A synchronous counter that consists of clocked flip-flops arranged as a shift register. Data is propagated from left to right (or from right to left) between the flip-flops by the application of a clock or count pulse. Counting is achieved by setting the contents of the shift register to logic 0 (or logic 1) and loading the leftmost (rightmost) flip-flop with a logic 1 (logic 0). An m-bit counter, which has m flip-flops, will then require m clock pulses to shift this 1 (or 0) to the rightmost (leftmost) flip-flop. The position in the register of the 1 (or 0) thus acts as a count of the number of pulses received since application of the load.

The counter may be made to count continuously by arranging that the output of the rightmost (leftmost) flip-flop sets the input of the leftmost (rightmost) flip-flop. The counter is then known as a ring counter.