Microcontrollers use various combinations of the logic circuits explained so far.
In the logic circuits introduced so far, if the input changes, the output changes at the same time. Its data cannot be stored.
On the other hand, a circuit that stores the information given in the past is called a sequential circuit (Feedback circuit).
The flip-flop circuit is the prototype of the storage circuit that is closely related to the microcontroller.
The word ”flip-flop” originally means "pitter-patter sound" or "the state changes suddenly".
Another name is also called a bi-stable multi vibrator.
As the name implies, it has two stable states. It is set by the input condition that determines one state.
This state is retained or stored until an input condition that determines the other states are given.
Flip-flops have RS, T, D, JK, etc., depending on how 0 and 1 are stored.