PCB Design Blogs

In one of the previous posts, we learnt about How to Run a RAVEL Rule from the GUI. The RAVEL rules that you write can be run from command line or Graphical User Interface (GUI) of Allegro® PCB Editor. You can also run these rules from Allegro® Constraint Manager.

This might get you thinking as to why prefer the complicated and dry command line over the ease and simplicity of GUI? Why remember and type commands when just clicking can enable you to do tasks directly?

In this post, we will talk about why and how to run these rules from command line.

Why run RAVEL rules from command line?

The command line comes with its own interpreted language rather than compiled language, that we generally use. The perks being that you get instant feedback. Since, the machine can interpret the command without having to compile, it saves time and hence, execution is faster. 

In the case of running RAVEL rules from command line, it is convenient for running batch checks where the user does not need to change constraint values or parameters while running the rules. It is also used for developing and debugging RAVEL rules efficiently.

On the other hand, running RAVEL rules from the GUI or from Allegro Constraint Manager allows the user to modify the parameters in the rule, while running it.

Now that we can determine when to use command line, let’s get started.

How to run RAVEL rules from command line

The command used to run these rules is ravel. All you have to do is, go to the command line and type ravel<space>RAVEL_file_name.rav.

The RAVEL file contains the rule, which usually has the constraints to be applied and checked for. However, users do not have permission to modify the values of the constraint parameters while running the rules.

Once you run the command, it will do its work and let you know if the constraints are followed or not. 

What happens in case there are any violations? 

The best part is that it reports errors on the command line itself, as soon as you run the command. 

In addition, the violations can also be identified on the design canvas by externally generated DRC Markers. To view the violations, choose Tools – DRC Browser. Expand External – Externally Determined Violation worksheet to see a list of all the DRC errors. Selecting a violation highlights it on the design canvas.

You can also check these violations in the DRC domain of Allegro Constraint Manager.

To learn in detail about this flow, watch the How to run a RAVEL Rule from the command line video on the Cadence Support portal. Click the video link now or visit Cadence Support and search for this video under Video Library.

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I hope this blog helps you in running RAVEL rules from the command line!