Discussion in 'Homework Help' started by ah_gal06, Jan 1, 2008.

1. ### ah_gal06 Thread Starter New Member

Jul 22, 2007
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0
i have a few qns for D Flip Flop..
1. if the clock is low, how it will affect the output?
2. if D is connected to NOT Q, what does it mean?

thanks a lot!

2. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Nothing will happen, the D-type flip flop is edge-triggered - in the absence of a clock edge the output will remain the same.

On successive clock-edges the input D and output Q will switch from one state to another, i.e. 0-1-0-1-0-1....

Dave

3. ### hgmjr Moderator

Jan 28, 2005
9,030
214
The end result of this connection scheme as dave has so ably stated is that the output of the latch divides the incoming clock signal by two.

hgmjr

4. ### ah_gal06 Thread Starter New Member

Jul 22, 2007
5
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huh? what is the meaning of divides the incoming clock signal by 2??

5. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
The outputs will change state at half the clock frequency.

6. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Oooppppssss!

Beenthere is correct. I should have used the term frequency in my reply.

Sorry for the confusion my omission may have created.

hgmjr

7. ### ah_gal06 Thread Starter New Member

Jul 22, 2007
5
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does it mean that NOT Q will send signal to D then Q will follow D?

sorry if i make u guys confuse.. the image is in the attachment. can u explain to me how the circuit works?

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8. ### hgmjr Moderator

Jan 28, 2005
9,030
214
Based on the diagram you have supplied, you can expect the Q output to change state with each depression of the switch. Some provision for de-bouncing the switch will need to be provided.

hgmjr

9. ### Dave Retired Moderator

Nov 17, 2003
6,960
145
Yes, but Q will only follow the change on D at the clock edge - this is a fundamental feature of flip-flops that differentiate them from other such devices such as latches.

For example: D is at 1 and at the clock-edge Q goes to 1 and NOT-Q goes to 0 - this 0 is fed back to D, however Q does not follow D and go to 0 until the clock changes again. It is a cyclic process that alters every time the clock changes.

Dave

10. ### ah_gal06 Thread Starter New Member

Jul 22, 2007
5
0
ok i think i understand.. thanks a lot for ur help!