RE: [SI-LIST] : The Skew control in ICX.

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From: Cusanelli, Tony (tony_cusanelli@mentorg.com)
Date: Tue Jul 11 2000 - 13:19:17 PDT


InMyung,

  When you add a variable time constraint to the spread
sheet ICX determines which line is the longest and sets
its real value as the MAX. (The Synthesizer can't move
the parts any closer together). It then performs any math
to determine the value for the minimum.

  In your case - let's say that the longest source to load
is 4 nanoseconds apart (note ICX uses time not length). A+1
would be set equal to 4, A would be 3 and any nets with less
than three nanoseconds delay would be flagged as failures.
The Synthesizer will then add copper to those nets in an attempt
to balance the skew.

  You can confirm this process if you look at the values that
are reported in the timing spread sheet.

 In your earlier post you asked about the following:

"Warning: A series resistor at design/1/pinInst/RA15-9 is not
attached to any other net."

   This will occur when you have two port devices in a module
and have not told the tool which ports are associated with each
other. For the example you showed, it looks like the resistors
go to a common pin. The IBIS model should use a 1k to ground or
VCC not a Rseries. (Someone else provided you with an Rseries model)
If indeed they are series resistors, you may need to add the ICX_SERIES
property to tell the tool which two ports are connected by the resistor.
The process is described in the manual.

Regards,
Tony

-----Original Message-----
From: In-myung Song [mailto:imsong@itx03.internex.co.kr]
Sent: Friday, July 07, 2000 1:27 AM
To: Signal Integrity News Group
Subject: [SI-LIST] : The Skew control in ICX.

Good morning everybody.

In korea, it is summer then very hot and sweat to be death.
The weather drive me crazy.

I have some question about skew control in ICX.
If there are some experts out of newsreaders, please help me.

I know that the skew control of specific nets means minimizing or
matching the propagation delay of
all the specific nets. right?
If then, when I control the skew in ICX, I set the a allowed. min delay
"a" and allowd, max delay "a+1" in timing rule sheet.
After synthesize of all the specific nets, when I open the timing rule
sheet the value of "a" is changed some specifc number, but the number is
bigger than allowed min. delay and smaller than allowed max. delay. Then
the min delay errors are occured.
I want to know why the value of "a" becomes one specific number and how
the ICX can calculate that number of "a".
And I want to know why the value of "a" is bigger that actual min.
delay.

Please help me.

 Inmyung Song.

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