RS flip flop -- Replacing a NOR gate with an OR gate

[Flying_Dutchman]

In the RS flip flops using a NOR gate if we replace the NOR by an OR gate all the outputs will be indeterminate. Both outputs Q and Q' will every time yield 1. Can you explain how the inputs 0 and 0 will give 1 1 as output

 

[256bits]

Try this,
Start with Set and Reset both being 1, and determine the outputs Q and Q-bar.
Then change either input ( or both ) to 0, and determine the outputs.

Start with Set and reset both being 0, and determine the outputs.
Change either input to a 1 ( or both ), and determine the outputs.

Repeat at your leisure.

 

[berkeman]

Adding a diagram to help the OP:

https://commons.wikimedia.org/wiki/File:RS_Flip-flop_(NOR).svg

 

[sophiecentaur]

Afaik, there's a general principle that a bistable circuit needs some Inverting Function in there. I guess you could also make a bistable with XOR gates but I don't have a handy pencil at the moment.

 

[Tom.G]

I guess you could also make a bistable with XOR gates but I don't have a handy pencil at the moment.

Please find a pencil and see if it can be done with two 2-input XOR gates.

 

[sophiecentaur]

Dang - I knew I'd be called out on this one!
No chance with just two XOR gates. But any solution has to have an inverting logic function.
I don't think there would be a solution with Diode-only Logic either.