Synchronous Counter
In synchronous counters we have the same clock signal to all the flipflops.
MOD4 Synchronous counter: We discuss here a 2bit synchronous counter. We have the circuit for this as:s
We have the initial outputs as Q0=0 & Q1=0. Whenever the first negative clock edge comes O/P of 1^{st} FF becomes 1 as we have J & K for 1^{st} FF as 1 and hence output of 1^{st} FF toggles and changes from 0 to 1. But when 1^{st} cock edge had come output of 1^{st} FF was 0. Hence J & K for 2^{nd} FF for 1^{st} edge are 0. So output of this FF doesn’t change and we get Q1=0. so the output is (Q1Q0)_{2}= 01_{2}.
On the next edge, output of 1^{st} FF changes from 1 to 0 as J & K are always 1 for this FF. Inputs for 2^{nd} edge for 2^{nd} FF are J=1 & K=1. Hence output changes from 0 to 1. so we get the count as (Q1Q0)_{2}= 10_{2}.
Similarly on the next edge we’ll get the output count as (Q1Q0)_{2}= 11_{2}.
And on the 4^{th} clock edge both the outputs get reset and we get the output as (Q1Q0)_{2}= 00_{2} and again whole procedure is repeated.
We’ll be studying other synchronous counter when we discuss the design of synchronous circuits later.
