What's Good About PCB SI Model Library Management? Look to SPB16.3 and See!

The SPB16.3 release of Design Entry HDL (DEHDL) provides an easier method for setting up the PCB SI model library path, and brings more consistency to the Front-to-Back (F2B) and Back-to-Front (B2F) flows.

Signal Integrity (SI) models are essential for running an SI simulation. PCB SI is an integrated solution with DEHDL and Allegro PCB Editor. When a design is moved from one engineer’s system to another engineer’s system, you need to ensure that the SI model PATH is correctly defined and available. Most of the time it is manually corrected. There is lot of confusion on how to effectively set the Device Modeling Language (DML) search paths and the preferences which configure simulation runs and retain data from one run to another, even when design is moved from one system to another. By setting up the SI Model path as a .cpm file directive you can set the models at the site level and make the design more portable.

Read on for more details …

Pre SPB16.3 behavior

• While setting up the search path for DML models:
  • Model File can be included
  • Model Library Path can be defined
    • All DML Models from the path are included
• SI model library paths defined are written in the folder signoise.run present at:
  • Physical folder – DEHDL
  • Project folder – Allegro System Architect (ASA)
• For the Front to Back flow:
  • All models in use are passed using pstdmlmodels.dat file.

Behavior in SPB16.3

• SI Model Setup information is stored in the .cpm file as directives:
  • SI_MODEL_PATH
    • List of directory paths to be searched for model files
    • Front End supports only DML files
  • SI_IGNORE_DML_LIBS
    • List of the library name to be ignored
  • SI_DML_WORKING_LIB
    • Working DML Library
    • New models will be saved here (e.g. auto generated models)
• Effect on Front to Back Flow
  • No change in the flow
  • SI Model Setup information passed to the env file in Allegro PCB Editor

Changes in the SI Model Setup UI

Only Library Paths can be added / deleted. The option to add / delete the dml and ndx file is removed.
New User interface for managing individual libraries (LM symbol in library setup):

 


The new Library Management  interface is used for the:

• Selection of  Working Library
• Selection of Libraries to Ignore
• Launching of Model Integrity

Migration from previous releases to SPB16.3

You need to run one of the following to move the SI model path defined in the previous release to the .cpm file directive.
In DEHDL automatic uprev on launch of:

• Model Assignment and saving it
• Constraint Manager and saving the data
• Running Export Physical

In ASA the design paths are read from the signoise.run folder and added to the .cpm file

Best Practices

• The SI model path should be defined at the site level
• If required, it can be locked at the site level

Diff Pair Renaming

With the SP16.3 release you can now change or modify the Diff Pair Name. For Model Defined and Library Defined Differential Pairs the Differential Pairs are automatically created on launching the Constraint Manager with a Tool Assigned name.

To rename a Diff Pair Name in Constraint Manager, select Diff Pair and Right Click Rename:



To revert back to a Tool Generated name, use the Use Default button.

New Properties effecting the CM flow:

• NO_DIFF_PAIR
  • Property on nets connected to Library / Model Defined Diff Pair Pins
  • Differential Pair between the Nets is not created
• NO_XNET_CONNECTION
  • Property on passive components with Signal Model definition
  • XNet is not created between the signals across the device

Looking forward to your feeback on using these new features.

Jerry "GenPart" Grzenia