Test by Bikram | Mock GATE | Test 3 | Question: 43

Question

The characteristic expression for a new $AB$-flip-flop is given below:

$Q_{n+1}$$\left ( A, B, Q_{n} \right )$ =  $\sim A \sim Q_{n}$ $+$  $B$$Q_{n}$  , where $\sim A$ means Not $A$ or $A$ $Bar$.
 

Identify the CORRECT statement among these:

• A.       If $A = 0, B = 0$ then flip flop resets.
• B.       If $A = 1, B = 0$ then flip flop retains the last value.
• C.       If $A = 0, B = 1$ then flip flop resets.
• D.       If $A = 0, B = 0$ then toggles.

Answer 1

Step 1: Draw K-map from the equation and identify the min-terms.

Step 2: From the minterms draw characteristic table.

Now, It can be easily seen that option D is true.

Comments

How do I know flip-flop resets or not from characteristic table? I did eliminate option B because q and $q_{n}$ are not same. In D q and $q_{n}$ are toggling, but not sure about A & C.