ISRO 2008-ECE - Ripple counter

Question

In a ripple counter how many changes in state happen when count changes from 7 to 8?
(a)$1$

(b)$2$

(c)$3$

(d)$4$

Answer 1

When change in count occurs in n-mod ripple counter from 7 to 8 the states of FF's can be decirbed as

0000...0111 to 0000....1000 hence 4 changes will occur.

Comments

how is it 4??

if it is a 3 -bit ripple counter then it will go from 000 to 111 then again 000 to 111..so 8 will surely not come.

and if it is a 4 bit ripple counter then,it will go from 0000... ,0110,0111,1000,1001..

so only 1 state change will be there,why from 7,it will go to 0 again??

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do u mean that from 0111 to 1000,each flip flop is toggled and hence 4 states are changed??but that is nt correct ..right??

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Yes that is what I mean to say and it is correct bcoz "count" is changing and not "state" from 7 to 8 and it is larger counter than one with 3 FF's bcoz of count value 8. You are assuming 3 FF's and change in "state" from 7 to 8 which is not correct.

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no,i am nt assuming 3 FF,i just gave it as an example that with 3 FF,we cant get 8.

counter shows us the count of clock pulss arriving at its input.

how can u say that toggling each flip flop values is same as 4 states changed??i dun get the relation

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Say I have counter with 5 FF-s and it has count value 7(00111) and it changes to 8(01000) last four flip flops changed their output or gou can say state. Take 6FF counter count changed from 000111 to 001000 so everytime last four FF's will change output rest will have unchanged output of 0.

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i got ur point but this is called change of state of flip flops.
anyways,thanks:)