Sequential Synchronous Circuit

Thread Starter


Joined May 27, 2020
I'm learning about sequential synchronous circuits, and I was trying to do an exercise, but I'm not going as I expected.

The exercise is about

  • Elaborate the excitation equation of flip-flops;
  • Write the output equation;
  • Say if it is a Moore or Mealy Machine;
  • Elaborate transition table and outputs;
  • Draw the state diagram;
enter image description here

I presume that A-B-C are outputs, so for Excitation Equation I tried:

D0 = Q1

D1 = Q2

D3 = ( Q2' + Q1') ^ (Q1 ^ Q0) "XOR -> ^"

View attachment 240272

Output Equation:

View attachment 240273

A = Q0
B = Q1
C = Q2

And I'm a little confused, if this circuit has no inputs this means that it is a Moore machine right? We can't say that a Mealy machine because taking into account a Mealy machine the Output is a function of current state and inputs, and in my output equations I don't have any input term right?!

I don't know if I did well the equations, if I don't can someone explain to me what and why? Thanks everyone!
Last edited:


Joined Feb 24, 2006
A Moore machine can have inputs but is not required to have them. It is a Moore machine by virtue of having the outputs be a function of the state only. That is they do not depend on how you got to a state, but only that you are in a particular state.