Synchronous Counters

Abstract

In synchronous counters, the counting sequence is controlled by means of a clock pulse and all the changes of the outputs of all flip-flops occur in synchronism. This effectively eliminates the large propagation delay associated with ripple-through counters, as mentioned in chapter 10. Master-slave flip-flops are invariably used in synchronous counters to avoid the possibility of oscillation and instability when feedback connections are made in the completed counter. In this mode of operation, the appropriate input signals are simultaneously gated into the master stages of all the flip-flops in the counter. When the input pulse falls to the ‘0’ level, the new values of the count are transmitted synchronously to the outputs of the flip-flops.