Flip Flops
Flip-flops are synchronous bistable devices. The term synchronous means the output changes state only when the clock input is triggered. That is, changes in the output occur in synchronization with the clock.
Flip-flop is a kind of multivibrator. There are three types of multivibrators: 1. Monostable multivibrator (also called one-shot) has only one stable state. It produces a single pulse in response to a triggering input. 2. Bistable multivibrator exhibits two stable states. It is able to retain the two SET and RESET states indefinitely. It is commonly used as a basic building block for counters, registers and memories. 3. Astable multivibrator has no stable state at all. It is used primarily as an oscillator to generate periodic pulse waveforms for timing purposes.
In this tutorial, the three basic categories of bistable elements are emphasized: edge-triggered flip-flop, pulse-triggered (master-slave) flip-flop, and data lock-out flip-flop. Their operating characteristics and basic applications will also be discussed.
An edge-triggered flip-flop changes states either at the positive edge (rising edge) or at the negative edge (falling edge) of the clock pulse on the control input. The three basic types are introduced here: S-R, J-K and D. | Click on one the following types of flip-flop. Then its logic symbol will be shown on the left. Notice the small triangle, called the dynamic input indicator, is used to identify an edge-triggered flip-flop. Positive edge-triggered (without bubble at Clock input):
S-R, J-K, and D. Negative edge-triggered (with bubble at Clock input):
S-R, J-K, and D. |
The S-R, J-K and D inputs are called synchronous inputs because data on these inputs are transferred to the flip-flop's output only on the triggering edge of the clock pulse.On the other hand, the direct set (SET) and clear (CLR) inputs are called asynchronous inputs, as they are inputs that affect the state of the flip-flop independent
Flip-flop is a kind of multivibrator. There are three types of multivibrators: 1. Monostable multivibrator (also called one-shot) has only one stable state. It produces a single pulse in response to a triggering input. 2. Bistable multivibrator exhibits two stable states. It is able to retain the two SET and RESET states indefinitely. It is commonly used as a basic building block for counters, registers and memories. 3. Astable multivibrator has no stable state at all. It is used primarily as an oscillator to generate periodic pulse waveforms for timing purposes.
In this tutorial, the three basic categories of bistable elements are emphasized: edge-triggered flip-flop, pulse-triggered (master-slave) flip-flop, and data lock-out flip-flop. Their operating characteristics and basic applications will also be discussed.
An edge-triggered flip-flop changes states either at the positive edge (rising edge) or at the negative edge (falling edge) of the clock pulse on the control input. The three basic types are introduced here: S-R, J-K and D. | Click on one the following types of flip-flop. Then its logic symbol will be shown on the left. Notice the small triangle, called the dynamic input indicator, is used to identify an edge-triggered flip-flop. Positive edge-triggered (without bubble at Clock input):
S-R, J-K, and D. Negative edge-triggered (with bubble at Clock input):
S-R, J-K, and D. |
The S-R, J-K and D inputs are called synchronous inputs because data on these inputs are transferred to the flip-flop's output only on the triggering edge of the clock pulse.On the other hand, the direct set (SET) and clear (CLR) inputs are called asynchronous inputs, as they are inputs that affect the state of the flip-flop independent