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4961 Discussions

when OR gates work as AND gates.!? NEEK

Altera_Forum
Honored Contributor I
907 Views

ok, I know its been a few years since I went to school but has someone redefined how OR gates work.!? 

 

(See attached) 

 

So I have two buttons on my NEEK connected to a OR2 gate. The output drives an led. 

 

so problem is you have to press BOTH to get the led to come on. 

 

I then tried swapping out the OR2 gate with an AND2 gate - guess what, either button lights the led.!?:confused: 

 

Any comments welcome. 

 

Thanks 

Paul 

 

Quartus 9.1 Build 222 Web Edition 

WinXP SP2
0 Kudos
4 Replies
Altera_Forum
Honored Contributor I
80 Views

Retry it with primitive AND, OR, instead of LPM_AND LPM_OR

Altera_Forum
Honored Contributor I
80 Views

Did you check the logic sense of your switches and LEDs??

Altera_Forum
Honored Contributor I
80 Views

Ha-ha-!! :D 

 

Yes its the logic on the buttons and leds. 

 

Buttons when pressed pull down and leds are pull down. 

 

Thanks for pointing out the obvious - silly me! 

 

Many thanks 

Paul :)
Altera_Forum
Honored Contributor I
80 Views

Congratulations, you have just discovered de morgan's laws (http://en.wikipedia.org/wiki/de_morgan%27s_laws) the hard way!

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