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I tried to simulate universal register in proteus software, for that purpose, I used 4052 component as a multiplexer (two of them actually, since one such component consists of two 4 to 1 multiplexers) and 40175 as a set of D flip flops. However, when I create this circuit, this is the warning I get:

enter image description here

Unfortunately, I failed to determine where \$V_{ee}\$ pin is actually located and what is the problem with it, but this is what happens with simulation:

enter image description here

As you can see, some sets of switches don't have their state (not even undefined), yet on the other hand, some of them seem to work just fine. What could cause this problem? Any help appreciated!

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  • \$\begingroup\$ Can you show your component list? And are you using the free (trial) version, or the full version? \$\endgroup\$ – MCG Apr 10 at 7:55
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The 4051 is an analog multiplexer. Using it for digital signals may work, but isn't recommended. Consider using a part along the lines of the 74xx153 instead. There is no reason to use 4000 series parts in this day and age; they've been obsolete for decades.

On these multiplexers, you're pulling the INH (inhibit) input high. This disables the analog switches entirely; any behavior you're seeing is likely due to floating-bus behavior. The INH input must be pulled low to enable the switches. (But, as I mentioned before, you should really use a digital multiplexer, not this analog one.)

The VEE error you're getting is related to this being an analog part. VEE is supposed to be a negative supply voltage. Proteus ignores this, but real ICs will require it.

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  • \$\begingroup\$ Thanks for the response, i tried the same with 74AS153, instead of the analog mux, however, i got error saying: "No model specified for U1" and "No model specified for U2". What is that supposed to mean? \$\endgroup\$ – cdummie Apr 10 at 9:35
  • \$\begingroup\$ @cdummie the 'no model specified' and other errors are a reason I asked if you could add a picture of your component list and also confirm whether you are using the free (trial) version or the full version. The "No model specified" error is what you get when there is no SPICE model for the component, so it cannot be simulated. Sometimes there are multiple versions of the same IC, not all have a SPICE model. The trial version also doesn't have the full library. Side note - The Vee pin is an irrelevant thing for the 4051 btw, the device will still work. \$\endgroup\$ – MCG Apr 10 at 10:40

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