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Re: gEDA-user: gschem sym files



I have seen this handled in other CAD packages not by making the pin an NC in the symbol, but by having a feature in the schematic where the pin can be "No Connect"ed so that it is not flagged as an error if it has no wire.

Or course, it makes some sense to have a special type of NC in a symbol if the data sheet says to not connect it. I have seen those. They often don't even tell you why. I think typically it is a factory use pin and they don't want any noise pickup. Grounding it would upset the operation of the chip so it just needs to float with as little copper as feasible. So either you should not be able to connect a wire to it (just make it a graphic pin and not a real pin) or flag an error if a connection is made.

Rick


At 12:24 PM 10/4/2010, you wrote:
>> Since nc is just a piece of copper attached to the (plastic/ceramic)
>> package, why should drc complain?
>>
>> A "nc" pin would be like "pas", but gives no error if unconnected.
>>
>The documentation of the Renesas TinyH8 states:
>"... Do not connect anything to the nc-pins. They might be used as test
>pins under certain conditions or used for damping purposes, which you don't
>,know."

This would imply that a 'nc' should prohibit any connections to it
whatsoever, so there is no chance of a connection, and that another type:
'don't care' or 'ignore' or 'unknown' or 'x' should be made that will not
give an error if unconnected, but will also not give an error IF connected.

>>> I would also like to see a pwr_src pin type which would be the output of
>>> the voltage regulator (or source).  That way the DRC would warn you if
>>> you shorted two power sources together or if you forgot to hook one of
>>> your power input pins to the power plane (and only connected it to a
>>> capacitor instead).
>> +1
>+1
Very useful.


Andrew Miner




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