Answer to Question #272562 in Electrical Engineering for Sylvia

Question

Design, using SR flip-flops and an external input x, a circuit that will count modulo 10 (i.e. from zero to nine, then back to zero and repeat). The circuit should only count when x = 1. If x = 0, there should be no change of state. Show all the steps involved.

 

a.     Draw the State diagram

b.     From the state diagram, derived the circuit excitation and output/state table

c.     Use K-maps to derive the necessary logic equations for the flip-flop inputs

d.     Draw the sequential circuit.

Answer 1

The number of flip-flops required to generate mod N ring counter is identified by the relation ,

now we are going to design mod 10 ring counter, so, we find n which satisfy the relation ,

So, n=4, satisfied the given equation.

Let's see the excitation table of SR flip-flops,

state transition diagram:

After S9 to S15 we will take it as don't care.

Now, we will solve the equation for S0, S1, S2, S3, R0, R1, R2, R3 using K-maps.

assuming the input of Q3 Q2 Q1 Q0 = A B C D.