ERC - Error found

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cleberdrums
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Joined: 17 Oct 2016, 11:46

ERC - Error found

#1 Post by cleberdrums » 30 Jun 2017, 10:02

When i run ERC some have some problem like ( Error - Short circuit: GND, U2:VSS - NetPort34:GND ) but i review everthing and dont have short circuit, then I make other schematic and I put GND with +5V and not get error with short circuit, thats is a bugs software or have some config wrong? Or just ignore this ... Someone could help me please. TKS
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Tomg
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Re: ERC - Error found

#2 Post by Tomg » 30 Jun 2017, 11:00

Can you show a screen shot of U2's "VSS" pin connection? (It is obscured by the rules table.) I'm guessing it is tied to the "GND" net.
Tom

cleberdrums
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Joined: 17 Oct 2016, 11:46

Re: ERC - Error found

#3 Post by cleberdrums » 30 Jun 2017, 12:45

Yep GND attached with VSS

-- 30 Jun 2017, 14:57 --



-- 30 Jun 2017, 14:57 --

I understood I need to rename VSS to GND the software does not recognize as GND

-- 30 Jun 2017, 15:01 --

But, when put GND with +5V, ERC don't show like a error ... Correct?
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Tomg
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Re: ERC - Error found

#4 Post by Tomg » 30 Jun 2017, 14:25

I believe the ERC will only check connections between component pins by comparing their "Electric" types (e.g. Power, Input, Output, Passive, etc). In the case of "Power" pins it checks to see if the names are different to be able to tell when, for example, "VCC" is connected to "GND". You can define a Net Port's "Electric" type, but the ERC apparently does not check Net Port names. That makes testing power Net Port connections as if they were component power pins impossible. So when one power Net Port gets connected to another power Net Port, the ERC will not flag it as an error. But when a component power pin gets connected to another component power pin with a different name, the ERC will flag it. I could be wrong, of course.

***EDIT***

The explanation above is flawed. See a corrected and, hopefully, more accurate explanation below.
Last edited by Tomg on 01 Jul 2017, 04:50, edited 1 time in total.
Tom

cleberdrums
Posts: 12
Joined: 17 Oct 2016, 11:46

Re: ERC - Error found

#5 Post by cleberdrums » 30 Jun 2017, 15:22

Thanks for help

Tomg
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Joined: 20 Jun 2015, 14:39

Re: ERC - Error found

#6 Post by Tomg » 01 Jul 2017, 04:48

After looking over the ERC tool I have discovered that my original explanation is flawed. Here's my new and correct (I hope) take on how the ERC short circuit test works...

The ERC checks for short circuits between power and ground pins only if a power/ground pin's name begins with one of the prefixes specified in the "Power Pins for SC" section located in the lower-right-hand corner of the Electrical Rules Setup dialog window. (Apparently, "SC" stands for Short Circuit.) The default power pin prefix setting is "V*", which means any power pin or power Netport whose name begins with "V" is tested as a power pin. The default ground pin prefix setting is "GND*", which means that any power pin or power Netport whose name begins with "GND" is tested as a ground pin. Any power pin whose name does not begin with either of these prefixes is not included in the "power pin to ground pin" short circuit test.

So if the name of your power NetPort begins with "V", then a connection made between it and a power NetPort whose name begins with "GND" would be caught and flagged. Unfortunately, it looks like the "Power:" and "Ground:" entry boxes will only accept one prefix so we're stuck with that limitation. It would be helpful if the user could specify more than one prefix (e.g. V*, +*, -*) to test not only power pins/NetPorts with names like "VCC", but other power pins/NetPorts with names like "+5V", "-15V", etc.

I'm definitely no expert on this subject so please let me know if the explanation above needs any corrections.
Tom

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