This simple latch works OK on my breadboard,but doesn't work on my simulator.Am I doing something wrong?

 

You probably need to connect the unused inputs of your OR-gate to ground.

hgmjr

 

The unused inputs are connected to ground,and it works OK on the breadboard.I cannot get it to work on my Logic Lab simulator.I thought I may be performing an illegal operation.I havn't seen this application used anywhere.

 

You drawing does not indicate that the unused inputs are tied to anything. That is why I replied as I did.

If your simulated device has its unused inputs tied to ground then it should work.

hgmjr

 

In real hardware, I suspect that the output will come up either high or low when power is switched on, depending on the internal circuitry. I'm not sure what simulator you are using, but unused inputs of behavioral gates in LTspice are automatically inactive, so grounding them wouldn't help..

 

Please define the phrase "doesn't work." Is the simulator output always low? Does it follow the input? Is the o/p an analog representation of a Barry Manilow tune?

 

I have attached the graph for both modes of operation.The breadboard version latches,the simulator vertion doesn't. Thanks for the prompt replies.

 

I screwed up. Here is the correct diagram

 

It works in my simulator, even using CMOS logic without having all of the unused inputs grounded. Perhaps you've found a bug in your simulator software.

 

It's a USB interface device called Digi-bee+ with simulating software called Logic-Lab plus I have just written to them hoping they can help me

Thanks for your help everyone

 

If it was behaving like an AND gate,the output would not go high at all

 

Pilko is correct. My goof.

hgmjr