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Below is a basic NOT circuit using a NAND gate.

enter image description here

Not sure why output is X, when I change Output properties to three state no, I can't modify circuit.

Sometimes, these issues go away when I restart Logisim.

some more weird issues...

My ALU output shows E

enter image description here

I tracked that down to below highlighted Mux gate

enter image description here

When I drill down to that gate it shows x on output enter image description here

When I tried to modify that, it gives this popup

enter image description here

when I click ok and try to change input, x in output will be gone.

All my subcircuits are fine individually, when combining them to make ALU, these kind of weird issues popup, when drilling down, we will see results like above.

Faced same issue with adder, but restarting Logisim fixed the issue.

Any ideas or pointers ...?

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1 Answer 1

Reset to default
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Make sure that simulation is enabled (in the Simulation menu). If simulation is disabled, the states of signals in your circuit will not be updated.

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  • \$\begingroup\$ Actually, the simulation is enabled and even when trying to change input to 1/0 doesnt change output \$\endgroup\$
    – TheGameiswar
    Commented Aug 15, 2019 at 2:49
  • \$\begingroup\$ when i closed this and reopened and it works.Getting strange errors like this \$\endgroup\$
    – TheGameiswar
    Commented Aug 15, 2019 at 2:49
  • \$\begingroup\$ Weird! That's the only way I was able to reproduce the result shown in your screenshot -- if simulation is enabled, a floating (blue) input to an AND gate would normally result in an undefined (red) output, not another floating output. \$\endgroup\$
    – user39382
    Commented Aug 15, 2019 at 2:52
  • \$\begingroup\$ Added some more data to question.Thanks for your time on this \$\endgroup\$
    – TheGameiswar
    Commented Aug 15, 2019 at 3:00

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