# Flip flopshe

Discussion in 'General Electronics Chat' started by harikanaidu, Apr 7, 2016.

1. ### harikanaidu Thread Starter Member

Nov 28, 2014
76
1
Hi,while i am reading about SR flip flop i studied that there will be some indeterminate state init...Can any one explain what this is?I want to know what are applications where we will use this SR flip flop...

2. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,442
1,628
It is in determinant because it has to be.

When you set the state of a flip flop it will remain in that state until you change it.

But what happens if you have never ever set that state? That is exactly true when the flip flop is first turned on, there is nothing to remember.

Practably if you build one in the real world it will tend to turn on in some repeatable pattern, but that is best determined by experiment, and no decent engineer would depend on that initial state anyway as it is dependent on some unknown or unknowable side effects.

So when used in the real world some extra circuitry will be added to set this initial state, unless that state matters not to the rest of the circuit.

It is the reason behind things like a "power on clear" pulse circuit, something to generate a reset signal when the power is first applied to set flip flops to a defined initial state.

shortbus likes this.
3. ### Marley Member

Apr 4, 2016
171
46
It depends on the exact type of flip-flop you are using and how it works inside.
But, because you have 2 inputs (S and R) you have 4 possible input states.
So looking at the truth table of all 4 states:-
S R Q
0 0 (remembers last state)
1 0 1
0 1 0
1 1 (possibly indeterminate - or could be 1 - depending on the internal circuit)

4. ### hp1729 Well-Known Member

Nov 23, 2015
2,105
235
Applications?
Design 322 uses a D-type latch as an SR latch in an electronic circuit breaker application.
Design 119 uses the SR latch to debounce switches
And yes, they can come up from power on in either state. You must plan for it. In Design 322 the latch deliberately comes up with the charger in the powered off state.

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