It’s Time to Modernize Debug Data and It’s Happening at DAC

“The leading edge is 1 million gates.” That was the news when we approved IEEE Verilog 1364-1995 and the open VCD syntax standard for debug data interoperability. Now the leading edge is over 1 billion gates and it’s time to modernize VCD. If you stop by the Verification Academy booth at DAC on Tuesday June 9 at 5pm, you’ll learn how.

Now that I’ve piqued your interest, lets take a look at why we need to do this. In the early 1990s, engineers were running RTL and gate designs on simulators and emulators that generated a large amount of debug data. They needed innovative tools to display and analyze this data, which meant they needed a way to decouple the data producers, simulators and emulators, from these new data-consuming technologies. The open Value Change Dump (VCD) text file syntax was defined for just this purpose. It is a simple means to identify signal names and the time/data pairs associated with them. VCD was then standardized within IEEE Verilog 1364-1995. The 1364-2001 extended VCD (eVCD) with signal strength information but retained the structure of the original syntax.

To say that things have changed is a massive understatement. Designs are 1000 times larger. We have complex test benches with object-oriented data types. We have power. VCD is still used for open interoperability, but the VCD files are too large and process too slowly to be used in most engineering flows. The industry created proprietary binary data formats that serve the data diversity and data size needs, but lost the producer/consumer decoupling that originally drove VCD.

Cadence and Mentor realized that it’s time to get debug data interoperability back. We are working on an open Debug Data API (DDA) to modernize VCD. The API defines a set of read functional calls enabling analysis tools to access binary data regardless of the source. The API will be provided as an open, Apache-licensed source code base so that tool providers can optimize the interface implementation for their tools. Doing so also preserves independence of the optimized binary databases in use today. As a result, the analysis tools can access raw debug data through from these binary databases through a single API with little overhead compared to the direct API associated with each one.

On April 28, 2015 Cadence announced third-party support with the new Indago Debug Platform. This collaborative work with Mentor is another step toward that goal. At DAC, you can learn more about the open DDA, the work completed so far, and the opportunities for the community to help us modernize VCD. Stop by the Verification Academy booth at 5pm on Tuesday to hear more about this collaboration and see a short demo.

Regards,

Adam Sherer