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STMicroelectronics - mixed analog-digital verification success with OVM

As long as the electronics industry is built on harnessing the laws of physics, the importance of analog signals will never go away. Nature speaks in waveforms, not regimented bitstreams. So the challenge, and one that must be repeatedly solved by those building ever more complex semiconductor devices, is how to verify what’s happening at the analog-digital interface.

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Questa® CDC Verification

We found the Mentor Graphics Questa ADMS tool to be the only one providing both a good level of analog accuracy that was required by our analog guys and seamless integration with our digital verification components and flow.”

Fabio Brognara, ST

ST needed to verify IP for a R/W channel to be integrated into a hard disk component (an SoC), and to do so with a verification process built from from reusable steps. Perhaps the biggest challenge was how to meaningfully work across analog and digital domains. Historically, engineers specialize and develop a set of skills relevant to just one domain. Digital verification engineers eschew graphics and spend most of their time writing and compiling vast amounts of code. By contrast, analog verification engineers look warily at code as most of their work is done via graphical interfaces. Though references to “mixed-mode simulation” abound, the phrase generally refers to implementing an analog design digitally, not truly working across domains.

The ST engineers kept their focus on integration into the larger SoC, not just on the IP. They made maximum use of standards, starting with OVM, and began writing verification components as soon as design work in RTL was underway. Key to their success: the Mentor Graphics Questa ADMS tool, which preserved analog accuracy while enabling easy integration into digital verification flow.

In analog only verification, the simulated patterns are often simple and fairly symmetrical, two characteristics that don’t describe the complex, sprawling and often asymmetrical waveforms produced by magnetic fields read from and written to a hard disk. By feeding the analog front end a pattern very similar to one that might actually be read from a disc, the ST team was able to find bugs in the analog domain missed by their colleagues working on the analog design.

Mentor Graphics helped us to quickly solve problems and they were proactive, too.”

Alberto Allara, ST

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