PrimeTime: Debugging Constraints

OVERVIEW

This workshop addresses the most time-consuming part of static timing analysis: debugging constraints. The workshop provides a method to identify potential timing problems, identify the cause, and determine the effects of these problems. Armed with this information, students will now be able to confirm that constraints are correct or, if incorrect, will have sufficient information to correct the problem.
Incorrect STA constraints must be identified because they obscure real timing violations and can cause two problems: either the real violations are missed and not reported or violations are reported that are not real, making it difficult to find the real violations hidden among them.
Following are three examples among many that students should be able to debug and resolve at the end of this workshop:

• Identify the specific registers in a design that are expecting but not receiving a clock, then determine a potential clock source for creating the missing clock. .
• An output port has been constrained but is not being exercised by PrimeTime because all timing paths to this port are broken. Identify where and why the paths have been broken in order to verify if the STA results will be correct and complete.
• Identify combinational loops in the design. Determine if the timing arc that is disabled automatically by PrimeTime breaks any valid timing paths, thus requiring dynamic loop breaking to be used during STA.
  Skills learned include:
  • Identifying constraint problems using three key PrimeTime commands: check_timing; report_analysis_coverage; report_timing.
  • Pinpointing the cause and determining the effects of constraint warnings through mastery of eight PrimeTime commands and a custom Tcl procedure: all_fanin; all_fanout; get_attribute; report_disable_timing; report_lib; report_cell; report_port; report_clock; report_case_propagation.
  Hands-on labs follow each training module, allowing students to apply the knowledge learned during the lecture to debug STA problems on a complex, unfamiliar design. Upon completion of the labs, students should have mastered constraint debugging skills that are essential when performing advanced analysis and debugging on any netlist.

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  This workshop is part of the Synopsys Designers' Edge Series targeted at the advanced user, who is facing difficult design challenges and wants to maximize productivity with Synopsys tools. These workshops include the most up-to-date tool and methodology information available.
  
  

  This workshop is also offered as part of the Synopsys Virtual Classroom: PrimeTime: Debugging Constraints .
  
  Please Note: This class was formerly delivered as: PrimeTime: Advanced STA Constraint Debugging.

  OBJECTIVES

  At the end of this workshop the student should be able to:

  • Pinpoint the cause and determine the effects of check_timing and report_analysis_coverage warnings
  • Execute seven PrimeTime commands and two custom procedures to trace from the warning to the cause and explore objects in that path
  • Systematically debug scripts to eliminate obvious problems using PrimeTime
  • Independently and fully utilize check_timing and report_analysis_coverage to flag remaining constraint problems
  • Identify key pieces of a timing report for debugging final constraint problems

  AUDIENCE PROFILE

  Design or Verification engineers who perform STA using PrimeTime.

  PREREQUISITES

  To benefit the most from the material presented in this workshop, you should:

  • Have taken PrimeTime 1

    OR

  • Possess equivalent knowledge with PrimeTime including:
    • Script writing using Tcl
    • Reading and linking a design
    • Writing block constraints
    • Generating and interpreting timing reports using report_timing and report_constraint commands

  COURSE OUTLINE

  Unit 1: Tools of the Trade

  • Lab 1 A Guided Tour of the Tools of the Trade
  • Lab 2 Choose the Correct Command and Apply It
    
  Unit 2: Complete Qualification of PrimeTime Inputs
  • Lab 3 Find and Debug Potential Constraint Problems

  SYNOPSYS TOOLS USED

  • PrimeTime 2007.06