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Non-sequential counter design

  • #1
JJBladester
Gold Member
286
2

Homework Statement



Hello, I need to create a digital counter that follows this sequence:


00, 10, 01, 11, 01, 00, 11, 10
A , C, B, D, B, A, D, C


Homework Equations



N/A

The Attempt at a Solution



There are four states (A = 00, B = 01, C = 10, D = 11) so I believe I need two flip-flops. There are eight transitions and then the counter should wrap. I'm having a hard time drawing the state diagram for this.

Here's what I have so far.

non-sequential-counter-state-diagram.jpg
 

Answers and Replies

  • #2
berkeman
Mentor
57,450
7,469
The sequence does not repeat in what you showed, so you will need to add another FF to tell you whether it's the first time through AC... or 2nd time through AD...
 
  • #3
LCKurtz
Science Advisor
Homework Helper
Insights Author
Gold Member
9,543
755

Homework Statement



Hello, I need to create a digital counter that follows this sequence:


00, 10, 01, 11, 01, 00, 11, 10
A , C, B, D, B, A, D, C


Homework Equations



N/A

The Attempt at a Solution



There are four states (A = 00, B = 01, C = 10, D = 11) so I believe I need two flip-flops. There are eight transitions and then the counter should wrap. I'm having a hard time drawing the state diagram for this.

Here's what I have so far.

non-sequential-counter-state-diagram.jpg
Hey Bladester, wasn't it a couple of years ago when you posted your first problem of this type? You must be about ready to graduate, eh?

I agree with Berkeman. You need 8 states instead of 4. Otherwise, for example, when the machine is in state A, how can it know whether to proceed to C or D next? So try:$$
y_2y_1y_0=000, 010, 001, 011, 101, 100, 111, 110, 000$$Then the output ##y_1y_0## gives you your sequence.
 

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