The toggle condition appears in J-K flip-flop when A. J=1, K=1 B. J=0, K=0 C. J=0, K=1 D. J=1, K=0 E. J=0, K=1 and J=1, K=0 Choose the correct answer from the options given below :
A only
The J-K flip-flop's four input combinations. Its characteristic equation is
\(Q_{n+1}=J\overline{Q_n}+\overline{K}Q_n\)
which gives the complete excitation table:
| J | K | Qn+1 | Action |
|---|---|---|---|
| 0 | 0 | Qn | Hold (no change) |
| 0 | 1 | 0 | Reset |
| 1 | 0 | 1 | Set |
| 1 | 1 | \(\overline{Q_n}\) | Toggle |
Check the toggle row against the equation. Putting J = K = 1:
\(Q_{n+1}=1\cdot\overline{Q_n}+\overline{1}\cdot Q_n=\overline{Q_n}\)
so the output complements on every active clock edge — that is the toggle condition, i.e. statement A.
Why the other statements are not toggle. B (J = K = 0) holds the previous state; C (J = 0, K = 1) forces a reset to 0; D (J = 1, K = 0) forces a set to 1. E merely pairs those set and reset conditions, so it is not toggle either.
Why this matters. The J = K = 1 state is the whole reason the J-K flip-flop was introduced: in an S-R flip-flop the equivalent input S = R = 1 is forbidden (indeterminate output), and the J-K's internal cross-coupled feedback turns that useless combination into a well-defined complement operation. Tying J and K permanently to 1 converts the device into a T (toggle) flip-flop, which divides the clock frequency by 2 and is the building block of ripple counters.
One practical caution. In a level-triggered (non-edge) J-K, holding J = K = 1 while the clock is high causes the output to oscillate repeatedly — the "race-around" problem — which is cured by edge-triggering or by the master–slave configuration.
Hence, the toggle condition occurs only for J = 1, K = 1, i.e. A only.
Similar Questions
The truth table of D flip-flop is given below:
C D Qn+1 O X Qn (Last State) $\uparrow$ 0 0 $\uparrow$ 1 1 Choose exact characteristic equation based on above Truth Table
Assertion (A) : Delay flip flop is used to store a single bit either 0 or 1.
Reason (R) : It has only one input, when clock is high and D input is also high, the output resets.
Assertion (A) : Asynchronous sequential circuit is also called event driven circuit.
Reason (R) : Event driven circuit does not have clock to trigger change of state. The states are changed by the change in input signal of the previous stage.
Select your answer using the codes given below.
For the circuit shown below consider the two statements :
Assertion (A) : The circuit is sequential.
Reason (R) : There is a loop in circuit.
Select your answer using the codes given below.
Flip Flop can be used to make :
(a) Latches
(b) Bounce-elimination switches
(c) ADDER
(d) Encoder
Which of the statements given above are correct ?
Under which input condition, the J-K Flip-Flop toggles ?
Read the following statements :
(a) In a J-K Flip Flop, if J = K, the resulting Flip Flop is referred to as a T-type Flip Flop
(b) In a J-K Flip Flop, if J ≠ K, the resulting Flip Flop is referred to as a D-type Flip Flop
(c) An S-R Flip Flop cannot be converted into a T-type Flip Flop since S = R = 1 is not allowed.Which is correct ?
Which of the following statements are true regarding the operation of JK flip-flop ?
1. When K input is low and J input is high, the Q output of the flip flop is reset.
2. When K input is high and J input is low, the output Q of the flip flop is set.
3. When both the inputs K and J are low, the output Q does not change.
4. When both the inputs K and J are high it is possible to set or reset the flip-flop (ie) the output toggle on next positive clock edge.Which one of the following is true ?
Assertion (A) : D-flip-flops are used as buffer register.
Reason (R) : Flip-flops are free from "race-around" condition.
Select your answer using the codes given below :
In the circuit shown below, the output Y1 and Y2 for the given initial condition Y1 = Y2 = 1 and after four input pulses will be
Important Questions from Sequential Circuits
A basic memory storage element in a digital system is:
The basic sequential logic building block in which the output follows the data input as long as the ENABLE input is active, is
What can be the maximum clock frequency of a 10-bit ripple counter which will not cause a count to skip, considering 10 ns propagation delay for each of the edge-triggered flip flops?
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