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62 DESIGN007 MAGAZINE I APRIL 2018 can be launched. However, in order to avoid producing a large number of violations in batch mode, the number of enabled rules can be initially limited. Further rules can be gradu- ally added to increase the scope as violations are eliminated. The scope of the checks can be defined using a specific group of design objects. I set up "User Objects" for DDR3, DDR3 ACC, DDR3 Data and USB which are similar to Net Classes in EDA tools (Figure 3). Then a DRC can be run on that particular group of signals, so that the violations can be checked in subsets, which simplifies the process. Alternatively, all DRCs can be run in batch mode and each violation can then be evaluated in succession (Figure 4). However, the individ- ual lists present more control over the param- eters. For instance, the differential impedance can be modified from 80ohms for DDR3 to 90ohms for USB between checks. Figure 5 shows the results of the uncoupled length check for differential pairs. This image highlights where the USB pair loses coupling and increases in impedance, so you can visual- ize where the variations occur. In this case, it is an acceptable violation. Keep in mind that the flagged violations are not necessarily errors. In this age of design complexity and limited time to market, there are always compromises that one has to accept due to schedule and other restrictions. HyperL- ynx DRC identifies violations of the established rules enabling the designer to quickly make a decision on the acceptability or not of the vio- lation. Once DRCs are completed, the errors can be selected individually, from the violation list- ing, for viewing. In addition, Sharelist reports containing the image, violation details, coordi- nates and user comments can be generated in HTML for broader team review. Additionally, customers have free access to the HyperLynx DRC Community. This forum provides the benefit of trouble shooting tech- nical issues and discussing ideas, with fellow designers, regardless of your layout tool, or level of expertise. HyperLynx DRC complements most EDA layout tools and does not require high-speed design expertise. It quickly identifies and high- lights possible design inconsistencies and puts Figure 5: Uncoupled length of differential pairs.

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