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 The Breker Trekker

Archive for May, 2016

The Power and Simplicity of Path Constraints

Wednesday, May 25th, 2016

Last week on The Breker Trekker, we talked about path constraints and how they differ from other kinds of constraints commonly used in SoC design and verification. Our whole approach to verification is based on graph-based scenario models, and constraints on the paths through the graph are a natural way to control how our Trek family of products automatically generates test cases. It’s easy to eliminate some paths, focus on others, or bias the randomization of selections. We believe that path constraints should be a part of any portable stimulus solution that meets the forthcoming Accellera standard.

We have heard some people in the industry argue that path constraints are not needed, and that value constraints would suffice. While we agree that value constraints are a familiar concept from the UVM and other constrained-random approaches, we do not feel that they are the best way to control the scenarios generated from a portable stimulus model. In today’s post we will expand on the example from last week and show how path constraints can handle a more complex design better than value constraints.

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Path Constraints for Graphs and Portable Stimulus

Thursday, May 19th, 2016

As engineers, we take great pride in defining our terms carefully and using them precisely to try to avoid ambiguity or confusion. Many engineering specifications start with a glossary of terms and sometimes even a taxonomy showing how they are related. Sometimes though, natural language being inherently ambiguous, we find that we have overloaded the meaning of certain words in a way that can lead to precisely the confusion we seek to avoid.

One such word is “constraint” because it is used in several different contexts in chip design and verification. In today’s post we would like to discuss path constraints on a graph-based scenario model. We will explain how they differ from other forms of constraints and why path constraints are essential for any portable stimulus solution, including the Trek family of products from Breker.

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SoCs in Space!

Wednesday, May 11th, 2016

The title of last week’s post was a play on a Mark Twain quote. This week I draw from a more contemporary source: The Muppets. Some episodes of the legendary family TV show featured a skit called “Pigs in Space.” In my head I’m reading “SoCs in Space!” with the same booming intonation used on the show for “Pigs in Space” to lead into a somewhat more serious discussion about the use of advanced chips in extreme conditions.

My prompt for this particular post came not from TV, but from an announcement yesterday that VORAGO Technologies is offering an ARM-based microcontroller (MCU) “designed specifically for radiation and extreme temperature operation without up-screening.” In other words, they ship an MCU that’s ready to use in such traditionally challenging environments as automobiles and industrial controllers as well as, yes, space. That got me thinking about even more complex chips such as SoCs and the extreme conditions they might have to face.

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The Report of Simulation’s Death Was an Exaggeration

Thursday, May 5th, 2016

With a nod to Mark Twain, this week I’d like to comment on a recent three-part series with the provocative title “Are Simulation’s Days Numbered?” The articles were transcribed from one of the “experts at the table” events that SemiconductorEngineering does so well. Breker wasn’t involved in this particular roundtable, but I enjoyed reading the series and found that it stirred up some thoughts. As a blogger, of course I’m going to share them with you and I hope you enjoy them in turn.

Let’s get this out of the way immediately: in three parts and more than 5,000 words, there was no mention of portable stimulus. That might not seem too surprising given the title, but in fact verification portability both from IP to system and from simulation to hardware arose during the discussion. So I’ll comment on that but, given my background as a vendor of formal EDA tools and reusable IP blocks, there are a few other topics that also piqued my interest.

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