## 24/03/2020

### Flip Flop Interview Question Answer - 1

In this post, most important questions of flip flops are given which includes difference between combinational circuit and sequential circuit, meaning of flip flop, bi-stable multivibrator, state of flip flops, gate latch, SR flip flop, resetting of flip flop, SR latch, clocked SR latch.

Describe the difference between combinational circuit and sequential circuit?

Combinational circuit

• The output at any time depends only upon present input at that time.
• The previous input condition does not affect the output
• No memory

Sequential circuit

• The output at any time depends only upon present input at that time as well as past input.
• It consists of memory.
• It is made of combinational circuit and memory elements.

Meaning of Flip Flop

Explain the term : Flip – flop

Flipflop

• It has two stable states that can be used to store information.
• The flip flops are made of logic gates.

Why the flip flop is also called as Bi – stable Multivibrator?

Bi – stable Multi vibrator

• The flip flop is called as Bi - stable multi vibrator because it has two stable states.
• The stable state can be changed by applying the proper triggering signal at the input.

State of Flip Flops

Which is the state of flip flops?

State of flip flop

• The state of the flip flop always indicates the state of normal output.
• A flip flop is said to be SET or HIGH or logic 1 state when the output is unity.
• A flip flop is said to be RESET or LOW or logic 0 states when the output is zero.

Which are the fundamental components of the shift registers and counters?

• Flip flops

Explain the term : Latch

Latch

• It is non – clocked flip flops. The output of the flip – flop latches 1 or 0 after applying input pulse.

Gate Latch

Explain the term : Gate Latch

Gate Latch

• The gate latch is a latch which responds to inputs when gate latch is on HIGH state and does not respond when it is LOW state.

Explain the meaning : Active Low input Latch and Active High input Latch

Active Low input Latch

• It means that SET and RESET are normally in the LOW state and one of them to be pulsed to HIGH state when we want to change latch outputs.

Active High input Latch

• It means that SET and RESET are normally in the HIGH state and one of them to be pulsed to LOW state when we want to change latch outputs.

SR Flip Flop

Which is simplest type of flip flop?

• S R flip flop

What is reason behind the name SR flip flop?

• There are two inputs SET ( S ) and RESET ( R ) in the flip flop so it is called as SR flip flop.

At which input condition the output of the RS flip flop is unpredictable or invalid or not - allowed?

NAND gate RS Flip flop ( Active High)

• When both inputs are High

NOR  gate RS Flip flop ( Active LOW)

• When both inputs are LOW

Which is other name of SR flip flop?

• Set – Clear Flip flop
• Set – Reset Flip flop

Resetting of Flip Flop

Why resetting of the flip flop is called as clearing?

• The resetting of the flip flop is called as clearing because the output 1 may be clearing by reset it to 0.

Why the gated S – R latch is called as asynchronous latch?

Gated S – R latch

• The output of the gated S – R latch changed at any time the input conditions are changed therefore it is called as asynchronous latch.

Why the gated S – R latch is called as clocked S – R latch?

Gated S – R latch

• The gated S – R latch has an ENABLE input.
• When the ENABLE input high, its S and R input control the state of the flip flop. As the ENABLE input low, the input becomes ineffective.
• The ENABLE input may clock therefore it is called as clocked S – R latch.