# Latches, Flip-Flops, and Timers MCQs

1. An active HIGH input S-R latch is formed by the cross-coupling of

(a) two NOR gates

(b) two NAND gates

(c) two OR gates

(d) two AND gates

3. For what combinations of the inputs D and EN will a D latch reset?

(a) D = LOW, EN = LOW
(b) D = LOW, EN = HIGH
(c) D = HIGH, EN = LOW
(d) D = HIGH, EN = HIGH

4. A flip-flop changes its state during the

(a) complete operational cycle
(b) falling edge of the clock pulse
(c) rising edge of the clock pulse
(d) both answers (b) and (c)

5. The purpose of the clock input to a flip-flop is to

(a) clear the device
(b) set the device
(c) always cause the output to change states
(d) cause the output to assume a state dependent on the controlling (J-K or D) inputs.

6. For an edge-triggered D flip-flop,

(a) a change in the state of the flip-flop can occur only at a clock pulse edge
(b) the state that the flip-flop goes to depends on the D input
(c) the output follows the input at each clock pulse
(d) all of these answers

7. A feature that distinguishes the J-K flip-flop from the D flip-flop is the

(a) toggle condition

(b) preset input

(c) type of clock

(d) clear input

8. A flip-flop is SET when

(a) J = 0, K = 0

(b) J = 0, K = 1

(c) J = 1, K = 0

(d) J = 1, K = 1

9. A J-K flip-flop with J = 1 and K = 1 has a 10 kHz clock input. The Q output is

(a) constantly HIGH

(b) constantly LOW

(c) a 10 kHz square wave

(d) a 5 kHz square wave

10. A one-shot is a type of

(a) monostable multivibrator

(b) astable multivibrator

(c) timer

(d) answers (a) and (c)

(e) answers (b) and (c)

11. The output pulse width of a nonretriggerable one-shot depends on

(a) the trigger intervals

(b) the supply voltage

(c) a resistor and capacitor

(d) the threshold voltage

12. An astable multivibrator

(a) requires a periodic trigger input

(b) has no stable state

(c) is an oscillator

(d) produces a periodic pulse output

(e) answers (a), (b), (c), and (d)

(f) answers (b), (c), and (d) only