What are flip-flops in digital electronics

Flip-flop / digital signal memory

Every electronic circuit that has two stable electrical states and can be switched from one state to another by means of corresponding input signals is called a flip-flop or bistable multivibrator. The flip-flop we are talking about here must not be confused with the fashionable bath slippers.


The different types of flip-flop are controlled differently, they have inputs that act differently and only change their state under certain specified conditions.
A simple flip-flop has two inputs and two outputs. Clock-dependent flip-flops also have a corresponding clock input C.
Flip-flops without a clock input are completely clock-independent. Your set and reset inputs can be addressed at any time.

Clock control of flip-flops


State-controlled flip-flop:

A state-controlled flip-flop whose set and reset inputs (1S and 1R) only become effective when a signal is present at the clock input (C1).


Single-edge controlled flip-flop:

A single-edge-controlled flip-flop whose set and reset inputs (1S and 1R) only take effect when the clock state is changed.
The susceptibility to interference from interfering signals is reduced by the short time of the clock edge.
The clock edge control is indicated in the circuit symbol by the triangle.


Two-state controlled flip-flop:

A two-state controlled flip-flop that receives the input states during one clock state and only outputs them in the next clock state.
Flip-flop outputs at which the input states appear delayed are called retarded outputs. Such flip-flops work on the master-slave principle. Recognizable by the right angle at the exit.


Two-edge controlled flip-flop:

A two-edge-controlled flip-flop that picks up the input states during a clock edge and only outputs them on the following edge.
In the case of the clock edge-controlled flip-flop, the susceptibility to interference is again reduced.
The clock edge control is indicated in the circuit symbol by the triangle.
Flip-flop outputs at which the input states appear delayed are called retarded outputs. Such flip-flops work on the master-slave principle. Recognizable by the right angle at the exit.

Identification of the entrances

The inputs of flip-flops are influenced in some way. Or rather, they are controlled. This control depends on the logic circuit that follows the input. The dependency is expressed by the identification of the input. The letter is followed by a 1 if the input is dominant.

  • G: AND dependency
  • V: OR dependency
  • C: tax dependency (cycle)
  • S: set dependency
  • R: reset dependency

Overview: flip-flops

The number of possible flip-flop circuits is very large. Listing all of these circuits would fill a huge number of pages. Therefore, the following remarks on the individual flip-flops only serve as a brief introduction. Only the most important flip-flops are considered.

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