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RTL analysis of FPGA using Grey Cell method

Posted: 28 Nov 2012 ?? ?Print Version ?Bookmark and Share

Keywords:RTL analysis? clock domain crossing? Verification?

As this module is being integrated within a bigger design, one may not want to keep all the details within the module. If the module is defined as a Grey Cell, all the elements within the red circle (figure 4) will NOT be included in the analysis thus enabling the designer to analyse bigger designs a lot faster. Let's note that the number of elements in the circle can be quite significant, meaning one can abstract a lot of design details as low level modules pass the RTL analysis checks.

When a module is declared as a Grey Cell, the Blue Pearl Software Suite will eliminate all register-to-register logic from the internal model, thus saving analysis effort and run time.

Figure 4: Module has fewer details when defined as Grey Cell.

Handling designs with large number of IP blocks
To illustrate the second issue described in the first section of this article, let's assume we have a design that contains numerous purchased IPs. The industry is rapidly demanding that IP sub-systems work well together to reduce time spent on integration and verification. As an example, a Memory IP sub-system would include the memory controller, the PHY and the Verification IP. Northwest Logic, one of Blue Pearl Software customers, is diligently working with its partners to perform this early verification however this is not a widely adopted practice today.

During chip assembly, if a designer considers the IPs to be black box (figure 1) the risk of having field failures is greatly increased. This is due to the fact that designs now have 10 to 50 clocks that drive these IPs, and many CDCs occur between the IPs. In the example below, CDC analysis with black boxes does not show any violation (figure 5) between the blocks.

Figure 5: Case where IPs are black-boxed.

When these IPs are defined as Grey Cells instead, the added details as compared to a Black Box, is sufficient to really find those troublesome issues that can crop up in the field. In this particular case, a CDC violation (figure 6) as indicated by the colour coded diagram below is found. This should help the designer take the corrective action early in the design cycle.

Figure 6: Analysis results using Grey Cell rather than black box.

Enabling Grey Cell
With the Grey Cell methodology, IP providers can be assured that the implementation of their design know-how is protected while it provides designers with a sophisticated method to catch issues before tape out. Designers can now catch those dreadful issues early in the flow while doing RTL analysis on bigger designs.

About the author
Shakeel Jeeawoody is Vice President of Marketing at Blue Pearl Software.

To download the PDF version of this article, click here.

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