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+8 votes

In a three stage counter, using RS flip flops what will be the value of the counter after giving $9$ pulses to its input? Assume that the value of counter before giving any pulses is 1.

  1. 1
  2. 2
  3. 9
  4. 10
in Digital Logic by Boss (30.8k points) | 2.8k views

2 Answers

+13 votes
Best answer

3 stage counter with RS FF is 3 bit counter, so after every 8 clock pulse, it will return to initial state.

Initial state is 1, state after 8 clock pulse will be 1, So, after 9th clock pulse , state will be 2. 

by Veteran (57k points)
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I think question is incomplete... its not given whether the counter is asynchronous or synchronus ?.. coz in both the cases answer will be different.
No, sequence of states doesn't depend on whether counter is synchronous or not
but no of states depends ..

for n bit conuter

1.for synchronous , total no of states possible = n  (Ring counter)

2. for synchronous , total no of states possible = n  (Johnson counter)

3. for asynchronous , total no of states possible = 2 Power n

ur solution is possible only by assuming case 3rd
1. n-bit synchronous counter, no of  states = 2^n

2. n-bit asynchronous counter, no of  states = 2^n

3. Ring counter and Johnson counter are special counters.
M getting confused here, i read that we can have mod N or mod 2N synchronous counter or mod 2^N asynchronous conuter using n bits.
the counter can represent from 0 to 7 right .. ? because its 3 bit ..

but since its starts with 1 , wont the states go like

1->2->3->4->5->6->7->1 (7 clock pulses)
0 votes

A three stage counter can count only to 8 (0-7)

Initially, count = 1.

After 9 clock pulses

$1\rightarrow 2\rightarrow 3\rightarrow 4\rightarrow 5\rightarrow 6\rightarrow 7\rightarrow 0\rightarrow 1\rightarrow 2$

Answer is 2

by Loyal (6.4k points)
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