# I have to design a 4-bit multi-mode counter circuit

Discussion in 'Homework Help' started by kstar1996, Jun 7, 2016.

1. ### kstar1996 Thread Starter New Member

Jun 7, 2016
7
0
using D flip flops, multiplexers, and combinational logic. The clock frequency of the counter circuit is 25 Mhz and here is the block diagram.

File size:
18 KB
Views:
8
2. ### dl324 AAC Fanatic!

Mar 30, 2015
7,083
1,628
Welcome to AAC!

Is this a homework question?

3. ### kstar1996 Thread Starter New Member

Jun 7, 2016
7
0
It's actually for a project! I have to start off by doing this to move on and do the other things... but I'm stuck from the beginning.

4. ### dl324 AAC Fanatic!

Mar 30, 2015
7,083
1,628
Is this a school project for which you will receive a grade?

5. ### kstar1996 Thread Starter New Member

Jun 7, 2016
7
0
Yes it is. I just need help for starting it off though... because it's due tommorow.
Is this right?

File size:
17.7 KB
Views:
8
6. ### dl324 AAC Fanatic!

Mar 30, 2015
7,083
1,628
You didn't allow enough time. AAC Members don't do the homework for you. Most problems take days to work through because we will only give you hints.

Is your counter supposed to be asynchronous or synchronous?

7. ### kstar1996 Thread Starter New Member

Jun 7, 2016
7
0
Actually it doesn't say anything about that in the problem. All it told me to do was what I wrote above.

8. ### dl324 AAC Fanatic!

Mar 30, 2015
7,083
1,628
What type of counters were you studying before this project was assigned?

Is it supposed to be binary or decade? What are the "multi-modes"?

9. ### kstar1996 Thread Starter New Member

Jun 7, 2016
7
0
Multimodes are just the same thing as up-down counters and it's supposed to be binary.

10. ### dl324 AAC Fanatic!

Mar 30, 2015
7,083
1,628
You have 4 inputs; is the counter supposed to have a load function? Is clear supposed to be synchronous or asynchronous?

11. ### kstar1996 Thread Starter New Member

Jun 7, 2016
7
0
Well this is all it gave in the problem other than what I said above.

File size:
18.4 KB
Views:
9
12. ### dl324 AAC Fanatic!

Mar 30, 2015
7,083
1,628
You have to do a synchronous counter design. Have you been studying excitation tables, transition tables, and Kmaps? Is clear supposed to be implemented? It's shown in the first picture, but not mentioned in the last post.

13. ### kstar1996 Thread Starter New Member

Jun 7, 2016
7
0
I'm sorry, but English isn't my first language so I can't understand by what you mean when you say "Is clear supposed to be implemented?" We did study Karnaugh Maps, transition tables, and I don't remember about excitation tables, but we probably did. I will just give the entire problem. I have to draw it using the SimUAid tool.

File size:
48.5 KB
Views:
7
14. ### dl324 AAC Fanatic!

Mar 30, 2015
7,083
1,628
The first thing you need to do is create an excitation table that will have 6 inputs. Have you studied how to simplify 6 variable Kmaps? Were you taught some short cuts to keep the Kmaps more manageable?

15. ### WBahn Moderator

Mar 31, 2012
22,981
6,878
This last one is what you should have started with. How can anyone help you when you tease out important parts of the problem in dribbles and drabs. Doesn't it seem reasonable that, for anyone to offer any assistance at all, that they would need to know what, exactly, each of the four most modes is. Also, does Gray Code and Right Shift really sound "just the same thing as up-down counters"? And notice that you don't need to implement a down counter at all.

There are a number of ways of tackling the problem. From a state machine standpoint, you have two inputs (assuming that we let the clear be asynchronous -- which may or may not be a valid assumption for your assignment) and four state variables. That's a six-variable K-map, which is about the largest that students are generally ever expected to deal with. But the fact that you are told to use multiplexers is a big hint as to another way of doing it: Design the logic for each of the four states separately and then use the multiplexers and the mode inputs to select which set of next state signals to use.

Now the ball is in your court -- we need to see a meaningful attempt on your part to work your problem. That gives us the necessary starting point from which to start. We will point out where you are going wrong and help guide you back to a path that heads you in the right direction. But YOU have to do the work. Leaving it to the night before it's due was a bad idea -- but if nothing else, perhaps it will teach you to not leave your homework until the night before it's due.