Circuit with an integrated FLIP FLOP

Thread Starter

tnn

Joined Jul 21, 2017
40
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.
 

MrChips

Joined Oct 2, 2009
21,119
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.
Sounds like a simple R-S flip-flop. You can use any such as 7474 or just two NAND gates.

1585576400893.png
 

Thread Starter

tnn

Joined Jul 21, 2017
40
I'll explain:
pin A is set to 1 when the circuit is powered.
Pin B is connected to a thermal switch that keeps pin 1.
When the thermal switch intervenes, pin C must go to 0 and must remain there even if the thermal switch closes again.
Pin C should return to 1 only when power is removed from the circuit and then switched back on and pin B is at 1.
 

MrChips

Joined Oct 2, 2009
21,119
Hah!
Now you have introduced a third condition. POWER-ON RESET.
You have to implement this behaviour explicitly in your circuit. It will not happen on its own.
 

Thread Starter

tnn

Joined Jul 21, 2017
40
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 …

Immagine1.jpg
 
Last edited:

MrChips

Joined Oct 2, 2009
21,119
Here is a simple POR circuit.

1585648387477.png

On POWER-ON the output signal /RESET is low.
After approximately RC seconds /RESET goes high. Use a logic gate to combine this with your A signal. You can also use diode logic.
 
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