On Apr 5, 2006, at 11:41 AM, Stuart Brorson wrote:
Place and connect to those pins the noconnection symbol
(misc/nc-*-1.sym). This will connect that pins to the net
"NoConnection", which is not checked in the DRC.
vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
However, be aware that
gnetlist and gsch2pcb will conect those non-connected pins together.
We have to find a way to avoid this, but it is to be done yet.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Actually, I am very disturbed by this, and have been for some time.
We encourage newbies to put a NC symbol on no-connect pins so the
design passes a DRC check. However, this symbol causes all the NC
pins
to be connected together. This is not a good idea, particularly since
it's an easy trap for newbies to get snared by.
Some NC pins are actually test pins on chips which shouldn't be
connected to anything lest some strange operational mode be triggered
in the chip.
I'd personally prefer that the DRC simply not report unconnected pins
-- a usually harmless thing -- than encourage a practice which can
inadvertently lead to bad boards simply to pass a DRC. The DRC is
supposed to prevent errors, not cause them! Perhaps disable this
feature until the appropriate fixes are rendered in the netlisting
backends and in gsch2pcb????
DRC is perhaps useful for large digital designs, but it is more
trouble than it's worth for small analog designs. The pintypes are
designed for digital, and often it isn't obvious what pintype you
want in analog. For example, for current mode interfaces the rules
about connecting inputs and outputs in parallel are reversed. There's
no way to distinguish between power *sources* and power *sinks*. Of
course you can designate everything passive, but then it's useless
(and that's still extra work).
Despite these limitations, gnetlist does a hard sell for DRC, as if
it was going to find lots of common problems when it really only
finds a restricted subset. We have newbies sweating to get DRC to
work for things like power supplies. That's silly.
John Doty Noqsi Aerospace, Ltd.
[EMAIL PROTECTED]
