[PCB_FORUM] Re: electrical constraint manager, timing

  • From: "Austin Franklin" <austin@xxxxxxxxxxxx>
  • To: <icu-pcb-forum@xxxxxxxxxxxxx>
  • Date: Tue, 5 Jul 2005 14:36:13 -0400

Hi Sam,

I can't help you with the autorouter...just the Constraint Manager and the
interactive router...  I think you have it set-up almost right.  Set PCLK in
Total Etch Length to 2500 min and 2700 max (that is your 2.5" =/- .2"...did
you mean =/- or +/-?), and then set-up a match group in relative propagation
delay with PCLK as your target.  But, I would set your group match length to
0:200 (delta of 0, tolerance of 200), and that should give you the length
match to +-200 to the target.

When you specify the tolerance in relative prop delay, you can set it in the
column for the group heading, and that applies it to the entire group...then
make sure PCLK is set to be the target.

Regards,

Austin

> Thanks Austin, I need the pclk to arrive to its destination a
> little before the data lines, i'm told the CLK line can be about
> 2.5 inches long =/- .200 inches. With those contraints i went to
> the NET folder under Total Etch Length i put min 2500 and max
> 2600 for pclk just to see how the router would do. Then i set up
> the relative prop delays with the data lines.
> I think i set those up correctly.
> I made the PCLK (2.5 in) the target and the data lines 200 mil:10
> mil. Which i'm told represents 200 mil longer or shorter than the
> 2.5 in PCLK.
> I did the pin pair and match group and i think everything is set
> up right, but when i push the autoroute button my total etch
> length are about 1000 mil over.
> thanks again for your time.
> Sam
> >
> > From: "Austin Franklin" <austin@xxxxxxxxxxxx>
> > Date: 2005/07/04 Mon PM 09:17:56 EDT
> > To: <icu-pcb-forum@xxxxxxxxxxxxx>
> > Subject: [PCB_FORUM] Re: electrical constraint manager, timing
> >
> > Hi Sam,
> >
> > > I set the clock up in in ecset in NETS folder.PCLK is set up to
> > > be 2300-2500 mils in length. The delta tolerance for the rest of
> > > the match group is 200mils =/- 10 mils. Yet when i auto route my
> > > clk is about 3000 mils and the rest fo the match group are about
> > > 4500 mils. Where do i set up the prop delay of the PCLK?
> >
> > I'm not clear on exactly what you are doing here, and perhaps
> on what you
> > are trying to do.  Do you want a relative delay group (all the
> signals are
> > simply relative to each other or to one signal...the target),
> or do you want
> > them to all be fixed lengths (between a min and a max absolute length)?
> >
> > It sounds to me (which is contrary to what I thought you
> wanted), that you
> > need specific lengths.  If you do, then you don't use relative
> prop delay,
> > but total etch length.  Let me know what you are trying to do, and I can
> > tell you how to do it.  I believe you only need to use one, total etch
> > length or relative prop delay.
> >
> > Regards,
> >
> > Austin
> >
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