![]() The characteristics of the counter are determined by the mode of interconnection between the flip-flops. ![]() Hence when ‘1’ is driven on the inputs of these flip-flops, they act as 1-bit counters (Figure 2). In counters the state is expected to change and not to remain tied-up to a particular value. Similarly for JK flip-flop output state remains either unchanged (for J = K = 0) or fixed to a particular value (0 for J = 0 and K = 1 1 for J = 1 and K = 0) for all cases expect when both of them are high. The reason behind this can be understood by the truth tables given by Table I.Ĭonsidering D flip-flop, it can be seen that the output changes only when the input is high. However to behave as counters, flip-flops must be driven by high (logic state 1) at their inputs, both in case of D as well as JK-types. Generalizing, one gets n-bit or mod-n counter of 2 n states counting from 0 to (2 n-1) by cascading n flip-flops. ![]() On the same grounds one can expect two flip-flops connected in series to form 2-bit counter counting from 0 to 3 comprising of 4 states and hence can be referred to as mod-4 counter. it counts from 0 to 1 and hence called modulo-2 (mod-2) counter. Thus a single flip-flop can track a count of two i.e. Although any flip-flop can be suitably connected to form a counter, most widely used are D and JK flip-flops (Figure 1).Īs known, flip-flops are bi-state devices, meaning they have two states, either zero (0) or one (1). In digital electronics counters are constructed using series of flip-flops. Counter is an electronic circuit used to count the number of times an event occurs.
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