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I suspect you’ve meant to use OR gate not XOR one.
Like on the following example:
http://www.allaboutcircuits.com/vol_4/chpt_10/4.html

You are welcome. Here what I’ve found. First I’ve been deleting from Test harness one by one: - Decoder symbol, try to power up: error. - 1 Bit Full Adder, try to power up: error. - Logical Unit, try to power up: error. - Main, try to power up: NO errors. Undo all changes. Now I know the erroneous c...

Hi John, The problem here is wiring of one of the AND gates on your adder (presumably the selected one). So to track it down, please click it on the diagram and look at the very bottom of the LC window. It should show you the name and position of the selected gate. So in this case you are looking fo...

Great, works like charm! It is very nice you’ve provided descriptions about the shifter as well as test harness. You can also add descriptions to input and output pins, so when mouse is hovered over, it is showing the details of the pin both on the circuit itself as well as on the symbol when you us...

Hi John,
Thank you for using LogicCircuit and willing to share your ideas and circuits with others. This board was created exactly for this purpose and you are always welcome to upload them here.
Good luck with your design creativity,
Eugene

Hi,
Thank you for sharing your thoughts and ideas. Adding comments to circuit is on radar for the next version.
Can you please explain what kind of hints did you get and how did you find them?
Thanks,
Eugene

Hi Peter,
Thank you for your suggestion. This feature is high priority for the next version.
In the meantime the tooltip is shown when you hovering your mouse over the pin.
Thanks,
Eugene

Sorry, this extension was not allowed. I’ve enabled it. Can you please try again?

Thank you for your wonderful contribution. Can you also upload the project file itself so people will just need to copy/paste what they want?

Hi Bill, There are could be either a bug in the program or you did not actually connected wire to pin. Please do the following: click the wire that is not working properly and see if it ends at the right places. If it is drawn correctly, then please save this file and send to me. You can attach it h...