delorie.com/archives/browse.cgi   search  
Mail Archives: geda-user/2015/07/18/19:44:43

X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f
X-Recipient: geda-user AT delorie DOT com
X-Envelope-From: paubert AT iram DOT es
Date: Sun, 19 Jul 2015 01:44:06 +0200
From: "Gabriel Paubert (paubert AT iram DOT es) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] Difference between attached and detached attributes
Message-ID: <20150718234406.GA14479@visitor2.iram.es>
References: <55A813B5 DOT 4040609 AT sbcglobal DOT net>
<alpine DOT DEB DOT 2 DOT 11 DOT 1507190000470 DOT 2893 AT nimbus>
MIME-Version: 1.0
In-Reply-To: <alpine.DEB.2.11.1507190000470.2893@nimbus>
User-Agent: Mutt/1.5.21 (2010-09-15)
X-Spamina-Bogosity: Unsure
X-Spamina-Spam-Score: -1.0 (-)
X-Spamina-Spam-Report: Content analysis details: (-1.0 points)
pts rule name description
---- ---------------------- --------------------------------------------------
-1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP
0.0 URIBL_BLOCKED ADMINISTRATOR NOTICE: The query to URIBL was blocked.
See
http://wiki.apache.org/spamassassin/DnsBlocklists#dnsbl-block
for more information.
[URIs: delorie.com]
-0.0 BAYES_40 BODY: Bayes spam probability is 20 to 40%
[score: 0.3402]
Reply-To: geda-user AT delorie DOT com
Errors-To: nobody AT delorie DOT com
X-Mailing-List: geda-user AT delorie DOT com
X-Unsubscribes-To: listserv AT delorie DOT com

On Sun, Jul 19, 2015 at 12:09:52AM +0200, Roland Lutz wrote:
> On Thu, 16 Jul 2015, Girvin R. Herr (gherr375 AT sbcglobal DOT net) [via geda-user AT delorie DOT com] wrote:
> >I have been doing some symbol work in gschem and I got confused
> >again about attached attributes vs detached attributes.  The
> >manuals do not go into detail about usage.  Hint, hint.  Can
> >someone tell me what is the difference between them and where I
> >should apply one vs the other?
> 
> An attribute is a specially formatted text object which can be
> attached to a component, net, bus, or pin, or not be attached at
> all.
> 
> An attribute which is not attached to an object is called a "floating" or
> "toplevel" attribute.  Floating attributes are used for two purposes: in a
> symbol, they contain default attribute values.  In a schematic, they
> contain information global to that schematic page; for example, the VHDL
> backend searches for a toplevel "module-name" attribute in the schematic,
> and John Doty's spice-noqsi backend searches for "spice-prolog" and
> "spice-epilog".
> 
> An attribute which is attached to a component overrides the value from the
> symbol's floating attribute.  (There are some exceptions to this like the
> "graphical=1" attribute which can't be properly unset by attaching an
> attribute to the component.)  You can delete an inherited attribute by
> attaching an attribute with the value "unknown" to the component.
> 
> You can't attach an attribute to a specific pin of a component's
> symbol, so you can't override pin attributes when you instantiate a
> symbol in a schematic.  There is a special slotting mechanism,
> though, which allows you to select one of a set of pre-defined pin
> numbering schemes.
> 
> It is important to understand that the attributes inherited from the
> symbol (both floating and attached to a pin) live in the symbol file,
> whereas the attributes attached to the component live in the instantiating
> schematic file.  You don't have a way to change the symbol from the
> instantiating schematic; the way to change inherited attributes is to
> attach an attribute with the same name and another value to the component.
> (You could obviously change the symbol by embedding it and hacking the
> schematic file, but AFAIK, there is no way to do this in gschem.)
> 
> When creating a component, some floating attributes from the symbol are
> usually copied to the schematic and automatically attached to the symbol,
> hiding the inherited attributes.  This is called "attribute promotion".
> The default set of promoted attributes is: footprint, device, value,
> model-name, and symversion.
> 
> The menu items "Attributes/Attach" and "Attributes/Detach" are used
> to attach floating attributes to components, nets, buses, and pins,
> and to convert attached attributes back to floating attributes.  You
> don't need these for normal gschem usage.  (If you still want to try
> them, take extra care not to accidentally lose invisible attributes.
> You can type "e n" to make invisible text temporarily visible.)

"e n" is a big hammer and often results in an extremely cluttered
display: if you select a component, typing "t t" will toggle the visibility
of the attributes of the component which is much less invasive. Typing
"t t" again obviously reverts the operation.

    Gabriel

- Raw text -


  webmaster     delorie software   privacy  
  Copyright © 2019   by DJ Delorie     Updated Jul 2019