Dear Protel Folks --

Here is a suggestion about signal name notation for active low logic states
that was taught to me by a wise old man some years ago.  I have adhered to
his rules whenever I have had the freedom to do so.  Here goes:

Never even attempt to put bars over the signal names, even if there is some
clever method provided by the schematic capture tool.  They can become
impossible to read when printed or passed to PDF files.  (The schematic tool
maker wants to please those who want to do bars over net names and thus sell
software.)  Place a tilde (~) after the signal name.  This way, read and
write will make complete sense with a slash as the delimiter, e.g., R/W~ or
W~/R and chip selects will look like CS~ and EN3~ and so on.

Never use a slash (/) or dash (-) or asterisk (*) to show negativity.  Never
place the negativity sign in front of the net name.  Always place it behind
the net name.

For bused signal groups that are active low, use ADDR~[7:0] and ADDR~0
ADDR~1 and so on.  There is no real need to force the negativity sign as the
last character, e.g., ADDR0~

Use the (-) dash to replace the underscore (_) in a complex net name, e.g.,
don't use FWD_MUX_CON but instead use FWD-MUX-CON

Don't use (*) asterisk as a suffix for negativity.  Use the tilde (~).
Instead, use the (*) asterisk as an AND operator in complex symbols, e.g.,
SEND * RESET~   In the same way, the (+) plus sign is the OR operator and
"(+)" including the parentheses is the EX-OR operator.

Use this convention on symbols and all net names.  I can guarantee that you
will NEVER print a Protel (or other) schematic, and/or make copies of same,
that will have signal name readability problems.  NEVER.  No lines on top of
net names, and no lines at the bottom of net names.  It is also true that
old habits about these things are hard to break.

Hope this helps!  Cheers!
-----------------------------------------
John R. Lemburg,    Sr. Hardware Engineer
Avistar Systems, Inc.,   Madison Building
15851 Dallas Parkway,   Suite #600
                       Addison, TX  75001
Direct 972-371-5708,  Main   972-361-6226
Fax    972-687-7014, [EMAIL PROTECTED]
-----------------------------------------


-----Original Message-----
From: TSListServer [mailto:[EMAIL PROTECTED]]On
Behalf Of Drew Lundsten
Sent: Wednesday, February 07, 2001 9:56 PM
To: Multiple recipients of list proteledausers
Subject: [PROTEL EDA USERS]: PDF and/or Postscript generation with
"over-bars"?



When we print schematics to .pdf using Acrobat Distiller or PDFWriter,
or to a generic Postscript printer (ours is a HP Laserjet 4050N),
"over-bar" symbols often disappear from a pin or net name and turn into
a much longer bar or line segment somewhere else on the same schematic
page. The result is that with a large page full of active-low signals,
the spurious over-bars make reading the schematic impossible - they look
like wire segments.

The installation in question is a P3-550/192M/Win2K/P99SE/SP5, and just
now confirmed with SP6. Protel tech support also confirmed the problem
on a sample schematic today, according to one of our engineers; it has
come up several times on various schematics of various sizes.

Has anyone else had printing problems with over-bars and if so, are
there any known solutions? My inclination is to always stick with a
leading - or # for active-low signals, but support and revision of
legacy designs is still a problem.

Thanks in advance,

Drew



* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*  This message sent by: PROTEL EDA USERS MAILING LIST
*
*  Use the "reply" command in your email program to
*  respond to this message.
*
*  To unsubscribe from this mailing list use the form at
*  the Association web site. You will need to give the same
*  email address you originally used to subscribe (do not
*  give an alias unless it was used to subscribe).
*
*  Visit http://www.techservinc.com/protelusers/subscrib.html
*  to unsubscribe or to subscribe a new email address.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *



* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*  This message sent by: PROTEL EDA USERS MAILING LIST
*
*  Use the "reply" command in your email program to
*  respond to this message.
*
*  To unsubscribe from this mailing list use the form at
*  the Association web site. You will need to give the same
*  email address you originally used to subscribe (do not
*  give an alias unless it was used to subscribe).
*
*  Visit http://www.techservinc.com/protelusers/subscrib.html
*  to unsubscribe or to subscribe a new email address.
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

________________________________________________________

To leave the EDAFORUM discussion list, send a email with
'leave edaforum' in the body to '[EMAIL PROTECTED]'

More Information : http://www.dolist.net

Reply via email to