SJTAG Newsletter


Issue 26 - Q4-2013

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Design Example Analysis

Regular readers will recall that in our last Newsletter we presented a design analysis example in the form of a block diagram and made reference to using "design patterns" and "templates" as a means to document our analyses of the design. It's probably worth expanding on that a little more and bringing you up-to-date with what this activity has revealed so far.

Design Patterns and Templates

Although the concept of design patterns was originally applied to architecture (by Christopher Alexander), the principles have been adopted in many fields. We have chosen to base our use on the methods commonly applied to object oriented software engineering. This reflects our belief that the main challenge facing SJTAG is one of software management rather than anything bound into the hardware we are testing.

A number of apparently distinct problems may fit a design pattern if they share a range of characteristics and traits such that the solving of each problem can be approached in the same way. Implementation details will obviously vary, but the method is the same across all problems conforming to the design pattern.

Description: Sample Template Form

Template Example

"Templates" are a means of documenting a "design pattern" in a tangible, readable form. These templates provide a common language and grammar to describe similar problem spaces to aid in identifying what characteristics may be common and where domains differ. For now, we are collecting these templates as simple text files in our wiki, but we intend to move them into a database in due course to help with searching and comparing templates.

Progress and Discoveries

We have worked up a small number of templates over recent weeks and while our first candidate, a structural test of the interconnect between a processor and a RAM, was relatively unremarkable, we unearthed a number of issues when we started to consider AC coupled data lanes between two devices. There were several subtly different methods that could be used to test those lanes: Some cases needed new templates but others were variations due to implementation choices and it is important that we construct the templates carefully so that we don't suffer an unnecessary explosion in the number of templates. From this, we are beginning to form some "rules" on best practice for completing templates and ways in which the templates themselves can be improved.

We hope these templates provide a basis to which others will be able to describe their problem domain based on their use cases. This information is quite necessary to aid in scoping the reaches of the SJTAG standardization effort. These templates also present a good educational resource that may be useful for academic research into how to manage tests over these various and sometimes conflicting problem domains. We feel it is imperative that we employ the test community in assisting with understanding the problems faced for testing at the board and system levels. Recently, there has been quite a bit of interest in this area now that IEEE 1149.1-2013 has been published with support for IEEE 1500. The recent balloting of the IEEE P1687 draft has also sparked renewed interest by the community. We hope you will join us by reviewing these templates and providing ones yourself as well.

The group is hoping to offer a brief insight into this work during the Board Test Workshop in December in order to gain some feedback on the value of this method.

Newsletter link:
Wiki link:

From the Chair

New look for our website and Newsletter

I'm sure you've already noticed, at least those of you who take the HTML version, that our newsletter looks a little different for this issue. While the layout is roughly similar to the last few issues, there's a new color scheme and a new, simpler logo for SJTAG - and it doesn't stop with the Newsletter.

Throughout October we've been working in the background to update and enhance the SJTAG website with the same clean, simplified look and a host of new usability features. We know that many of you can't join our conference calls and our website is the main way you stay informed on SJTAG activities. We wanted to make it as easy as possible for you to stay informed by introducing:

  • Mobile device support
  • Better site navigation

Read more on the website:

We hope you find these improvements helpful!



There are several newsfeeds available on the SJTAG website. On the main site, you can obtain feeds from:

The forums offer a range of feeds at the overall board, forum or individual discussion thread level to suit your preferences, while our wiki supplies a feed from the Recent Changes page.

Description: News Feed

Next Newsletter

The Q1-2014 edition of this newsletter will be published towards the end of January 2014. Copies of past newsletters are always available on the SJTAG website.

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