[Magic-dev] magic highlights "reset" nodes

[R. Timothy Edwards]

Dear Clint,

> Since I started using magic 7.3 and 7.4, I have noticed that sometimes
> nodes that are labeled with names containing "reset" in them (like
> "_reset", "reset", "reseta", etc.) sometimes show up with their labels
> in blue.  Then when I select such a node, it is shown as connected to
> other nodes with similar labels, even though they aren't electrically
> connected.
> 
> I assume that this is some kind of feature.  Is there some way to turn 
> it off?

Blue (cyan, to be pedantic) labels are "ports", and if magic were working
correctly, then they wouldn't show up unless you created them from
labels with the "port" command.  I'm skeptical that there is anything
special about the "reset" string.  What happens (and I just figured it
out this evening) is that due to a mismatch between the type declarations
for the label structure and its equivalent record for the "undo/redo"
mechanism, magic fouls up one of the subroutine calls.  If a label is
deleted and then undeleted by using the "undo" command, then it can
reappear as a label (the tile type information which records which
type the label is attached to is trashed, which may cause other problems
as well).

Ports do have the property that ports with the same name are treated
as electrically connected.  This allows one to create a standard cell
with "thru" ports (by giving the entrance and exit points the same
label name) and therefore trace an entire network through a standard
cell layout even if the contents of the standard cells are not drawn.
Another use is to trace a network through buffers that have been
inserted into the path by giving the buffer input and output ports
the same name.

Since I finally tracked down the bug, I also fixed it, of course, and
the corrected version is available from CVS and from the tarballs of
versions 7.4.16 and 7.5.15 (which will be automatically posted
tonight at 2:40 am pacific daylight time).

					Regards,
					Tim

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| Dr. R. Timothy Edwards (Tim)   | email: tim.edwards at multigig.com     |
| MultiGiG, Inc.                 | web:   http://www.multigig.com      |
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