Homebrew PCBs

It happens in the "real" world too, I'm afraid.

Donald.
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----- Original Message -----

> From: "Andrew Hakman" <andrew.hakman@...>
> To: "Homebrew PCBs" <Homebrew_PCBs@yahoogroups.com>
> Cc: "designer_craig" <cs6061@...>
> Sent: Sunday, February 20, 2011 1:56:45 AM
> Subject: Re: [Homebrew_PCBs] Re: NETS
> 
> On Sat, Feb 19, 2011 at 6:22 PM, designer_craig <cs6061@...>
> wrote:
> 
> >
> >
> > Yes, if you connect a new component pin up to a existing net becomes
> part
> > of the net. There is an exception in the PCB layout program. It is
> sometimes
> > possible to run some copper tracts that would allow you to short
> two
> > different nets. This can happen in a hand rout situation but the
> post layout
> > design rule checks should flag this.
> >
> > Sometimes its desirable to connect two nets together, like for
> example a
> > signal ground net connecting to a chassis ground net. You have
> component
> > pins on each net but want them connected together only at one point
> on the
> > layout for signal integrity reasons. So some packages have a
> virtual
> > component you place on the schematic, it has two pins one connected
> to each
> > net. No actual component is put on the board it just allows you to
> connect
> > the two nets without the DRC's complaining that you have shorted the
> nets.
> >
> 
> Heh, and if you're a *HDL designer / ASIC person, you got to watch out
> for
> those pesky "wire patches" that connect 2 nets together - no component
> gets
> placed in the design either, and they lead to all kinds of interesting
> fun
> if you skip some automated check steps (because the tech kit doesn't
> work
> properly with the verification tools, and there's no time to fix it
> before
> the deadline), like completely dead ASICs - OOPS! The project I'm
> working on
> has had at least 3 completely DOA ASIC runs, due to issues around
> connecting
> different nets together! Good thing it's just grad school - in the
> real
> world, I'm sure people would've been fired! Probably especially in the
> 2
> cases where VDD got inadvertantly connected to GND - yay, we built a
> $5000
> heater!
> 
> Andrew
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
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