- 26th October 2009, 21:09 #1

- Join Date
- Dec 2008
- Posts
- 17
- Helped
- 4 / 4
- Points
- 1,056
- Level
- 7

## designing a 4 bit counter

how do i design a 4 bit counter using d flip flops

thanks

- 26th October 2009, 21:09

- 26th October 2009, 21:45 #2

- Join Date
- Apr 2006
- Posts
- 31
- Helped
- 6 / 6
- Points
- 1,454
- Level
- 8

## Re: designing a 4 bit counter

I assume you want a synchronous counter - Use the D flip flop excitation table and draw up your circuit excitation table with your present and next states. Use Karnaugh maps to solve for your D value for each flip flop(4 in your case 'coz it's a 4-bit counter).

Here's a solution actually:

http://www.csci.csusb.edu/schubert/t...f03/dw4bit.pdf

- 26th October 2009, 21:45

- 26th October 2009, 22:10 #3

- Join Date
- Dec 2008
- Posts
- 17
- Helped
- 4 / 4
- Points
- 1,056
- Level
- 7

## Re: designing a 4 bit counter

Thanks alot

But what if I am constrained with 4 flipflops and only 3 logic gates

Do you have any idea how this will work??

Will it contain some sort of special feature ?

Thanks alot again

- 26th October 2009, 22:10

- 26th October 2009, 23:09 #4

- Join Date
- Apr 2006
- Posts
- 31
- Helped
- 6 / 6
- Points
- 1,454
- Level
- 8

## Re: designing a 4 bit counter

What exactly are your design needs? The reason I ask is you can design a 4-bit asynchronous counter with just four D flip flops. If you have a requirement that states - count from (0000)b to (1100)b and not (1111)b, then you use NAND gates to asynchronously clear inputs of all flip flops once your counter reaches (1100)b. You could make a case for a similar asynch design which would use 4 FFs and 3 logic gates.

- 27th October 2009, 00:03 #5

- Join Date
- Dec 2008
- Posts
- 17
- Helped
- 4 / 4
- Points
- 1,056
- Level
- 7

## Re: designing a 4 bit counter

my only constraint is that the counter consists of 4 d flip flops and any 3 logic gates

I will try to implement it to count to 1100 as you told me

I hope it works

Thanks alot

Added after 45 minutes:

I am really sorry

but can a counter count only even numbers??

I am really sorry for the disturbance but I can't figure it out

Thanks

- 27th October 2009, 15:30 #6

- Join Date
- Apr 2006
- Posts
- 31
- Helped
- 6 / 6
- Points
- 1,454
- Level
- 8

## Re: designing a 4 bit counter

Yup, you can design a synchronous four bit even counter. Draw up your state table with your present and next states, use the D-flip flop excitation table and karnaugh maps and extract your D value for each of the flip flops and you have your even counter! I am not sure how many logic gates it will use though, maybe you can reduce it down to three gates...