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Leverage ESL with legacy RTL

Posted: 18 Sep 2006 ?? ?Print Version ?Bookmark and Share

Keywords:John Wilson? Mentor Graphics? silicon? EDA? RTL?

As SoC complexity grows, designers are turning to esl methodologies to create next-generation designs.

Designers might hesitate to use ESL because of legacy RTL intellectual-property (IP) libraries that represent thousands of man-years of invested time. But legacy RTL IP can be the basis for new designs that leverage ESL methodologies.

Designers who have tried ESL design recognize that some parts of a design are more conducive to ESL, while others are more efficiently implemented using established IP libraries. Typically, ESL is used to create new, differentiated system components; RTL IP is best for the obligatory non-differentiated parts of the design.

These two methods are different aspects of a holistic electronic-system design methodology.

ESL does not replace RTL design. Instead, the ESL design flow extends RTL flows into higher levels of abstraction, much as RTL design extends gate-level design.

Platform-based design lets designers automatically integrate ESL modules with existing RTL IP. Platform-based design is made more effective when it uses Spirit XML data books from the Spirit Consortium to describe the IP. These data books include configuration and validation information to help determine the processes that must be executed to integrate the block into SoC design.


  • Consider the advantages of a platform-based design methodology, which automatically integrates complex IP into a system design quickly, shortening design cycles and allowing teams to focus on differentiated parts of the design.

  • Seek IP that includes XML files following the latest Spirit Consortium standard. The Spirit Consortium enables IP creators to write a machine-readable IP data book documenting many aspects of that IP, including information about simulation models, software, documentation and assertions. Different EDA tools can use Spirit XML-based IP files to automate various aspects of the design creation.

  • Create new RTL IP blocks intended for reuse, and document the IP in XML according to the latest Spirit standard. IP that is documented using the Spirit standard will be easier to deploy and reuse in new designs.

  • Extend your Spirit XML-based IP with generators. Generators are specialized code modules attached to IP or designs that understand the context in which the IP exists. Generators embed expert knowledge for designers to use in a design.

  • Check to ensure that your workplace has access to the most current Spirit XML libraries. A good place to start is


  • Purchase new IP that does not include Spirit XML data books. To maximize the productivity benefits of ESL design, designers must demand Spirit XML data books as a requirement for all merchant IP.

  • Forget that tools exist to automatically create Spirit data books for your existing IP. Creating these data books seems like an overwhelming task, especially for large libraries of RTL IP. The right tool can smooth the transition to platform-based design and automatic IP assembly.

  • Try to create Spirit XML data books for your entire RTL IP library all at once. Instead, focus on the most frequently used blocks to maximize the return-on-investment of your existing in-house IP.

  • Expect that a platform-based design methodology will yield a size-optimized final SoC design. Designers who use platform-based design can configure and connect IP using standard SoC buses, but must accept some design overhead, because not all IP functionality will be custom-created for the design.

  • Approach a platform-based design methodology as the end-all, cure-all for designing complicated systems that require complex IP. By itself, Spirit XML-based IP will not instantly ensure that your design flow fully integrates ESL and RTL aspects of your desired system. Selecting the right design environment is crucial.

- John Wilson
Product Engineer, Mentor Graphics Corp.

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