# Need help to design a counter that follows a given sequence using D Flip Flops

Discussion in 'Homework Help' started by dragstang86, Nov 11, 2010.

1. ### dragstang86 Thread Starter New Member

Nov 11, 2010
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0
I need to design a counter diagram that follows a count sequence 0-2-4-1-0 using DFFs.

The characteristic equation for the DFF is Q+ = D. I have the sequence in the present state and next state table but don't know where to go from there.

Code ( (Unknown Language)):
1.
2. Present State | Next State|Da |Db |Dc |
3. 000           | 010       | 0 | 1 | 0
4. 010           | 100       | 1 | 1 | 0
5. 100           | 001       | 1 | 0 | 1
6. 001           | 011       | 0 | 1 | 0
7. 011           | 000       | 0 | 1 | 1
8.
I appreciate any help. I have been trying to find a similar example for hours with no luck.

I think what the main thing I need help with is how to go from the state table to the k-map. If what I have done in the state table is correct. So I guess the first question is, is my state table correct?

Last edited by a moderator: Nov 11, 2010

Apr 5, 2008
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3. ### beenthere Retired Moderator

Apr 20, 2004
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dragstang86 likes this.
4. ### dragstang86 Thread Starter New Member

Nov 11, 2010
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Thanks! The 3 shouldn't be in there. I mixed the numbers up with a state graph that I just put together that used that sequence. I couldn't figure out how to edit my post but it should read:

Present State | Next State|Da |Db |Dc |
000 | 010 | 0 | 1 | 0
010 | 100 | 1 | 1 | 0
100 | 001 | 1 | 0 | 1
001 | 000 | 0 | 0 | 1

5. ### dragstang86 Thread Starter New Member

Nov 11, 2010
5
0
Thanks for the suggestion. I read that thread but it is more involved than my problem and I'm not quite at that point yet in my circuit knowledge. I am just now trying to learn the basics of these flip flops.

Apr 5, 2008
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Hello,

In the eBook at the top, there is this page on D flip-flops:

An other page with a lot of links is this one on the EDUCYPEDIA:
http://www.educypedia.be/electronics/digitalflipflops.htm

There are more pages like that over there on other digital subjects:

Digital electronics:
Arithmetic circuits D/A-A/D converters Number systems Codes and decoders Flip flops Technology Counters and registers General overview Technology-CMOS Digital logic Memories Technology-TTL Timers and oscillators

Bertus

7. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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Isn't this just a 3-bit shift register,
with outputs Q1, Q2, Q3
ordered as q2, q1, q3
?

8. ### Georacer Moderator

Nov 25, 2009
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1,266
4-bit actually; zero counts as information. It's a clever idea but usually homework assignments are very specific on the implementation methods.

9. ### djsfantasi AAC Fanatic!

Apr 11, 2010
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880
I figured out the 4-bit requirement, but didn't edit the post because I thought I had provided enough information for the OP.