# Circuit with an integrated FLIP FLOP

#### tnnelectro

Apr 5, 2012
54
Hello everyone,

I have to make a small circuit with an integrated FLIP FLOP that has this function:

1. pin A and B input to 1, pin C output goes to 1
2. when pin A is 1 and pin B is 0, pin C goes to 0 and remains there even if pin B returns to 1
3. pin C returns to 1 only when pin A goes from 1 to 0 and then to 1 again and with pin B to 1

how could I do? Help thanks.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Take a look at the operations of a couple of flip flops and see if you can find a match.

Remember that there are quite a few inputs, and A/B could be any two, and the output C could be either of the outputs. If there are more than 2 inputs your going to have to figure out what to do with the other inputs.

Have a close look at how the inputs are described. There is a clue there that will make your search a lot easier.

#### AnalogKid

Jun 10, 2015
2,670
Start by making a chart called a truth table with three columns: A and B for the inputs, and C for the output. List all possible combinations of A and B, and the resulting C condition for each one. Many flipflop datasheets have tables like this to summarize operations.

ak

#### tnnelectro

Apr 5, 2012
54
Can you give me an example of circuit ...

At power on, C goes to 1 if A and B are at 1.
After if B goes from 1 to 0, C goes to 0 and stays there until there is a reset of the circuit….

I hope this is clearer …

Last edited:

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Not clearer at all.

I understood the original description (did you?)

What types of flip-flops are you familiar with?

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
12,713
Looks like homework, so I moved this thread.

Why is there a timing involved in the table in post #4? Timing is not part of your description and needs additional circuitry to achieve.

Your flip-flop obviously has a SET function and a RESET function.That should get you started.

#### tnnelectro

Apr 5, 2012
54
Could I kindly have an example of a circuit to start from?
this is the state diagram

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
Do you know what a flip-flop is?

#### tnnelectro

Apr 5, 2012
54
Do you know what a flip-flop is?
an elementary circuit able to maintain the state in which it is found, or change it based on the inputs ..

I don't have much experience about it ...
But is the diagram clear?

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
12,713
But is the diagram clear?
If you label the states and the transitions with the correct signals associated, then yes.

Learn about flip-flops, start e.g. here for an introduction.

#### tnnelectro

Apr 5, 2012
54
If you label the states and the transitions with the correct signals associated, then yes.
but I reviewed them but for me they are correct ...

However, in the meantime, it made it simpler, that is, with the evergreen NE555 and two transistors ...

What do you think?

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
12,713
What do you think?
If the circuit works (I have no time to analyze it in detail), it is a solution to the original task description. It is very likely not the answer your instructor is looking for. You should really read up on flip-flops.

#### Nanren888

Nov 8, 2015
623
Your original description does not seem to have any concept of time. That is, some aspects are instantaneous, these input cause that to happen, others ate remembering state until something happens. Your circuit appears to have a one-second timer in it. Not clear that his has anything to do with your original request.
Is the 555 intended to debounce your switch?
The description just talks about levels, 0 and 1, rather than switches.
.
Result:
Did you have a look at the flip-fop references as suggested above?

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