Wednesday, December 03, 2008     Register | Login | Search | Contact Us
     
   
     
     

Many of you already received communications about the move of the Cadence user community into cadence.com. And many of you have already joined, with over 4000 registrations in the first two weeks.

The new Cadence Community enhances the ability of Cadence users to connect and collaborate. In addition to moving the community into cadence.com -- enabling single sign-on for community, Sourcelink and Cadence events -- the new site is organized around nine technology segments, giving you easy access to product information, training, forums and blogs. Some of the new features include:
  • Ability to respond to posts via e-mail
  • Technology-specific blogs
  • Latest Web 2.0 social networking capabilities
  • Public profile options
  • Private messaging
  • Friends lists
Visit the new Cadence Community today at www.cadence.com/community and join the discussions!

Registration note: Due to the scope of the enhancements and the new SSO registration system, we were not able to migrate existing cdnusers.org member accounts. So new registrations are required, but this enables a broader set of functionality we think you'll enjoy.

Forum note: Under the guidance of forum moderators, we have taken the 20+ cdnusers.org forums and consolidated them into 11 forums on the new site. Posts have been brought over so you can leverage that posting history. CDNusers forums will be set to read only starting 7/30, and cdnusers.org will be redirected to the new community on 8/4.

Best regards,
Mike and Tom

Michael A. Catrambone - Steering Committee Chairman
Distinguished Engineer
PCB/Mechanical
UTStarcom, Inc.

Tom Diederich
Cadence Community Manager
Home
Forums
Forums > Digital IC > Formal verification

Subject: TIP OF THE MONTH: Oct. 2007: level shifter checking
Posting to forums is available to community members only.
Login or Register
Rate this topic:
   
Author Messages
vksingh
Posts: 1
Online: User is Offline
10/08/2007 1:37 PM  
TIP OF THE MONTH: level shifter checking Here is a question that recur often with our Conformal Low Power (CLP) users: How can I disable or ignore level shifter checking on select signals that cross the voltage domain boundary? Level shifters are used in multiple supply voltage (MSV) designs to transport a data signal from one voltage value to a higher or a lower level. Since level shifters are characterized for the different voltages they operate between, the user should choose the correct level shifter cells for all appropriate voltage domain pair. A Low-to-High level shifter prevents excessive short circuit current in the CMOS device that it drives. A High-to-Lowlevel shifter is inserted to achieve safe timing closure.
Level shifters checks can be disabled by setting the appropriate switch in the run script.
For example, With the following command, any crossing from 1.2 V to 1.0 V domain will be ignored. However, a crossing from 1.2 V to 0.8 V domain will be flagged since the voltage difference between the two domains is 0.4 V, and that exceeds the tolerance value of 0.2 V specified in the command below: 
set lowpower option -ignore_high_to_low 0.2

The "ignore_low_to_high" option works similarly for crossings from low to high voltage domains.

The following command only checks for the existence of a level shifter and verifies that the power connections are correct. The numeric voltage values on the nets that are connected to the level shifter are ignored: 
set lowpower option -level_shifter_check connect


The warning and error messages can be filtered out using the 'add rule filter' and the 'add rule waiver' commands. These commands are not limited to level shifters and can also be used for violations reported on other low power structures: 
add rule filter R1 -rule LSH1.1 -message LS_LH
   report rule check LSH1.1
Here 'LS_LH' is the textual search string, and CLP will filter out any LSH1.1 violation MESsage that contains it.
Caution: The correct combination of boolean operators should be used to prevent unintended filtering of results.
The following command will filter out only those LSH3 messages that contain the strings "u123" and "DLAT_UDP": 
add rule filter R2 -rule LSH3 -MES u123 -AND -MES DLAT_UDP

To remove message number 6, 10 and 12 from the LSH3 report, use the following command: 
add rule waiver LSH3 6 10 12

Please see the 'Verify' manuals for more information.
Posting to forums is available to community members only.
Login or Register
Forums > Digital IC > Formal verification > TIP OF THE MONTH: Oct. 2007: level shifter checking


ActiveForums 3.6
     
Copyright 2006 Cadence Design Systems, Inc.