The flip flop

Task 17

The flip flop, or bistable multivibrator, is an important basic electronic circuit. It generally represents a storage location for a bit. Thousands of these circuits are used in microprocessors, and they are the basic circuit for dynamic RAM modules. The flip flop is also known as a flip flop multivibrator.

Today, flip flops are only attached to individual transistors in exceptional cases. There are a large range of integrated circuits that contain one or more of these switches.

The following logic table shows the correlations between signals on the inputs and the two outputs. This is the simplest form of flip flop, the RS flip flop. The name is derived from the two inputs.

S	R	Q1	Q2	Remarks
1	0	1	0	Set
0	0	X	X	Last stored state
0	1	0	1	Reset
1	1	0	0	Only as long as signal is applied, cannot be saved

The flip flop frequently has two outputs. The second output is then negated. This means that the opposite logical signal is always present. The negation is indicated by the small circle.

If one of the two inputs is activated with a logical signal, this is transferred to the output and saved. If there are no signals on the inputs, this state is retained. Only a signal on input R can reset the output. If both inputs are occupied with signals, this is an undesirable state. After the signals are removed, the output will remain set or reset depending on the shutdown sequence.

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