[PCB_FORUM] Re: Diff pair Constraints and CM
- From: "Andrew Noonan" <andrew@xxxxxxxxxxx>
- To: <icu-pcb-forum@xxxxxxxxxxxxx>
- Date: Thu, 10 Mar 2005 13:49:28 -0800
Kevin,
This is not necessarily true for diff pair stuff, when you have
different widths and spacing for different layers. For instance, outer
layers tend to have different spacing characteristics than inner layers
(not always.. but for the point of illustration).
In this case, you would NOT enter the values in the Electrical
constraints/Diff pair area, but back in Physical constraints, where
we're all used to doing it. The important thing here is that you would
simply leave those entries blank in the Electrical constraints/Diff pair
setup.
Most important to get the DRC's to report properly is to make sure there
is an entry for minimum line spacing for the Entire Design's diff pairs;
i.e., Minimum you would find anywhere in your design.
Hope this helps,
Andrew
-----Original Message-----
From: Kevin McCowan [mailto:kmccowan@xxxxxxxxxxxxxx]
Sent: Thursday, March 10, 2005 1:41 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: Diff pair Constraints and CM
Plus you don't set the diff pair stuff with
net_physical_type. You use constraints>electrical
constraints. This is the new way starting with version 15.
You did not specify which version you are using.
Net_ph and net_space are for group to group spacings.
And for constraint area spacing and widths.
Kevin McCowan
Sr. PCB Designer
TSI telsys
Reade, Sue wrote:
> As best as I can figure this out. The "constraints" form overrides the
> CM. So if you'd like all of the diff pairs to obey the same rules on
all
> layers, use CM first and only. If you have different gaps and widths
on
> different layers use "constraints". Setting gap is just one of those
> things you have to do manually.
>
> -----Original Message-----
> From: Dave Seymour [mailto:deseymour-pcb@xxxxxxxxxxxxx]
> Sent: Thursday, March 10, 2005 4:05 PM
> To: icu-pcb-forum@xxxxxxxxxxxxx
> Subject: [PCB_FORUM] Diff pair Constraints and CM
>
> Fresh 15.2 design.
>
> I assign a diff pair to two nets.
>
> Set the diff pair spacing in the NET_PHYSICAL_TYPE = DIFF with to
> 11mils. Neck witdh, gap all set.
>
> Assign the DIFF property to the nets.
>
> Assignment table correct.
>
> Nets route at 11mil space. Tracks obey all parameters.
>
> Great.
>
> How come the the 11 mil gap (etc) does not show in the CM on the DIFF
> page?
>
> Thanks
> Dave
>
> --
> Dave Seymour, CID+
> Catapult Communications Inc.
> 800 Perimeter Park Dr, Suite A
> Morrisville, NC 27560
>
> Direct: (919)653-4249
> Main: (919)653-4180
> Fax: (919)653-4297
>
> Dave.seymour@xxxxxxxxxxxx
>
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