[PCB_FORUM] Re: Using an "Electrical CSET" vs a "Constraint Set" for diff pairs...
- From: "Austin Franklin" <allegrolist@xxxxxxxxxxxx>
- To: <icu-pcb-forum@xxxxxxxxxxxxx>
- Date: Wed, 26 Mar 2008 16:31:23 -0500
Hi Gerry,
Yes, I thought that was what Gary was asking as well. I posted how TO do it
and was just wondering if there was a way to do it with CM. As a note, when
you put the diff pair phase tolerance in the spreadsheet, it actually
attaches a property to the net.
Best Regards,
Austin
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of Gerry Meier
Sent: Wednesday, March 26, 2008 2:08 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Using an "Electrical CSET" vs a "Constraint Set"
for diff pairs...
Austin,
"I'm not asking how to do anything", I thought someone (Maybe Not You) was
asking how to handle different trace width and gaps for diff pairs. This
works in 15.2 all the way through 15.7. There are parameters that need to be
in CM spreadsheet or an Ecset like min line width, tolerance settings.
Gerry
Gerry Meier, Sr. PCB Designer
Freedom CAD Services. Inc
Voice: (256)776-7470 or (603) 864-1350
Email:gerry.meier@xxxxxxxxxxxxxx
visit us at http://www.freedomcad.com
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From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Austin Franklin
Sent: Wednesday, March 26, 2008 2:52 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Using an "Electrical CSET" vs a "Constraint Set"
for diff pairs...
Hi Gary,
> I'm not sure how to handle a different trace width and spacing within
the pair for inner layers as opposed to outer layers.
I use Setup/Constraints and under "Physical (lines/vias) rule set" I use
"Set values..." and create a new Constraint Set Name, and set the values for
each layer there. Close that, then use "Attach property, nets..." and
assign the attribute "NET_PHYSICAL_TYPE" to all the nets I want to control
with this constraint.
That's the only way to do different trace width/gap on different layers
that I know of in Allegro 15.2. Is that what you were asking?
Unfortunately, I don't always have the luxury of having the same width/gap
for inner and outer layers.
Regards,
Austin
-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx]On Behalf Of Macindoe, Gary
Sent: Wednesday, March 26, 2008 1:18 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Using an "Electrical CSET" vs a "Constraint
Set" for diff pairs...
Hey Austin,
You know, I've wondered about that. Luckily I haven't had to deal with
it yet.
One reason is that lately I only have top and bottom as routing layers.
I think the last time I had inner layers, the stack-up was designed to
have the trace widths/spaces the same for inner and outer for all
impedances.
Here's how I handle it now for only outer routing layers, on 15.5.1:
- I set up the diff pairs using Logic -> Assign Differential
Pair, Auto Generate
- I set the trace width, spacing etc. for the pairs in CM
- I create a Spacing Constraint Set for each impedance (i.e.
"90DIFF" for USB) with the "Line To Line" set to the spacing required pair
to pair
I'm not sure how to handle a different trace width and spacing within
the pair for inner layers as opposed to outer layers.
I would suggest, if you can, to design the stack-up to have the widths
and spacings the same for outer and inner.
That's the easy way out!
Maybe setting up constraints, including diff pairs, is easier in 16, I
hope so.
Good luck, I'm curious to see if anyone has the solution to this.
Gary E. MacIndoe
PCB Design Engineer
Fort Collins, Colorado
amd.com
gary.macindoe@xxxxxxxxxxxxxxxxxxxx Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of Austin Franklin
Sent: Wednesday, March 26, 2008 12:39 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Using an "Electrical CSET" vs a "Constraint Set"
for diff pairs...
Hi,
There appear to be two ways to get the diff pair spacing and gap, but
only
one allows differing them by layer. Setting up an "Electrical CSET"
only
seems to allow one overall (as in for all layers) space/gap. But, the
advantage of using the ECSET is you can assign it to a net or multiple
nets
using the Constraints Manager spreadsheet using a pulldown menu.
Or, I can setup a "Constraint Set" and select each layer's
space/gap...but I
then have to attach this as a property to each and every net manually by
selecting the nets and attaching this Constraint Set name as a
NET_PHYSICAL_TYPE attribute.
I prefer the Constraint Set, since it gives me the per layer
control...but
the thing that seems to be missing, is the ability to assign a given
Constraint Set to the nets using the Constraint Manager spreadsheet.
I'm on 15.2. Am I missing something? If not, has this improved on 15.7
or
16?
Regards,
Austin
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