Скачать или смотреть How to Pass an Array of Parameters to Multiple Instances in Verilog Efficiently

Learn how to effectively instantiate multiple blocks in Verilog by passing an array of parameters to different instances without the need for additional hierarchy.
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Understanding the Challenge of Passing an Array of Parameters in Verilog

When working with Verilog, many engineers encounter issues when trying to pass packed arrays of parameters to multiple instances of the same block. This challenge can be particularly frustrating, as it leads to unexpected behavior, particularly with parameter propagation among instances.

In this article, we dive into a specific question related to this topic: How to correctly instantiate multiple foo_dp_top modules within foo_top, while passing individual items of N_CHAN and PORT_TYPE arrays?

The Problem Overview

The user presented a testbench and a design unit (DUT) setup, showing a scenario where multiple instances of a module are desired, and each instance should receive different values from the provided arrays. Here’s a simplified breakdown of what they aimed to achieve:

Instantiation: Dynamically instantiate N_DPORT instances of foo_dp_top.

Parameter Passing: Pass each instance an individual value from the N_CHAN and PORT_TYPE arrays.

However, while the first instance received the correct parameter, subsequent instances were not getting distinct values, leading to incorrect functionality.

Why the Issue Arises

In Verilog, when you instantiate an array of modules, all instances share the same parameters unless explicitly defined otherwise. This is because the parameters need to have uniform values across the instantiated modules.

So, when the user attempted to pass varying parameters directly from the arrays N_CHAN and PORT_TYPE, the first instance's parameters propagated to all instances. Hence, every instance received the same parameter values, leading to errors in functionality.

Suggested Solution: Using Generate Constructs

To efficiently solve this matter, you can utilize the generate construct in Verilog. This construct allows you to create parameterized instances of modules while customizing their parameters per instance. Here’s how to do it:

Step 1: Utilize the Generate Statement

You need to adjust the foo_top instantiation to leverage the genvar and generate constructs:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Key Points of This Approach

Dynamic Instances: By utilizing a for loop inside the generate block, you can create multiple instances dynamically while passing unique parameters.

Eliminating Extra Hierarchy: While this uses a generate block, it doesn't add extraneous level of hierarchy like traditional loops might, which would create a more complex design.

Maintaining Clarity: The clear specification of parameters corresponding to each instance maintains your design's readability and functionality.

Conclusion

In summary, while there can be challenges associated with passing arrays of parameters to module instances in Verilog, using a generate construct is an effective solution. This method allows you to create multiple parameterized instances neatly and without adding unnecessary complexity to your code.

By understanding the behavior of parameter passing in Verilog and leveraging a proper construct like generate, you can resolve these issues and build more robust hardware designs.



Feel free to reach out with any further questions, and happy coding in Verilog!