Timing Closure with Design Assistant

Introduction

In this article, we will explore the Design Assistant feature in Intel's Quartus Prime software, specifically focusing on its role in achieving timing closure in digital designs. The Design Assistant offers a powerful way to streamline the design process by highlighting potential issues that could affect your design's performance.

What is Design Assistant?

When enabled, the Design Assistant reports any violations against a standard set of recommended design rules, commonly referred to as DRCs (Design Rule Checks). This feature is designed to enhance productivity by minimizing the number of design iterations required to achieve design closure.

The Design Assistant includes rules from multiple categories such as clock linking and floor planning. However, we will particularly focus on time enclosure-related rules, which identify specific violations that can lead to timing failures in your design.

Timing Closure Rules Explained

The timing closure rules work intuitively. First, they check if your design has a bad topology based on the selected design closure rules. Next, the rules analyze the top 1000 setup-related paths. Only when these two criteria are violated will the design assistant report timing system violations.

This systematic approach results in fewer false positives, as you only receive notifications for violations that can genuinely affect timing, leaving out any unnecessary alerts for portions of the design that meet timing requirements.

To enable these timing-related rules, simply filter the rule names using the alphanumeric ID beginning with "TMC202".

Example Workflow for Timing Closure

Let's walk through a typical workflow in the conventional timing closure process:

1. Review Timing Analyzer Report: Begin by examining the timing analyzer report panel to ascertain whether the design meets the timing requirements.
2. Identify Timing Failures: If there are timing failures, launch the Timing Analyzer GUI for further details on the failing paths.
3. Cross-Probe the Netlist Viewer: For instance, if a specific design component, like a RAM block, shows a large micro TCO value, this might indicate that its output is unregistered. Cross-probing the netlist viewer confirms this issue.
4. Address the Problem: Users can then proceed to address the identified problems, such as registering the output of the RAM block.

With the Design Assistant, however, this process can be significantly simplified. By leveraging the timing enclosure-related rules, you can identify problems in the background without manually going through each step. With clear recommendations on what issues to resolve, users can efficiently secure timing closure.

Conclusion

In summary, the introduction of timing closure-related rules in the Design Assistant allows you to review reports without needing to access additional tools like fast-forward recommendation reports or the timing analyzer. The Design Assistant highlights the precise issues in your design, enabling a quicker and more focused route to achieving design closure, all while minimizing irrelevant alerts.

Thank you for taking the time to read about the Design Assistant and its importance in timing closure. We hope you find this tool useful in your design processes.

Keywords

Design Assistant, Timing Closure, Design Rules, DRCs, Timing Analyzer, Quartus Prime, Timing Violations, Micro TCO, Netlist Viewer.

FAQ

Q1: What is the purpose of the Design Assistant in the Quartus Prime software?
A1: The Design Assistant helps users identify violations against design rules, enhancing productivity and reducing the number of design iterations needed for timing closure.

Q2: How do timing closure rules work?
A2: Timing closure rules assess the design's topology and analyze the top 1000 setup-related paths to confirm whether violations exist that may lead to timing failures.

Q3: How can I enable timing-related rules in the Design Assistant?
A3: You can enable these rules by filtering the rule names using the alphanumeric ID that starts with "TMC202".

Q4: What steps are involved in addressing timing failures?
A4: The conventional steps include reviewing the timing analyzer report, identifying failures, cross-probing the netlist viewer for details, and making necessary changes to the design.

Q5: How does the Design Assistant minimize false positives?
A5: By only reporting potential violations that impact timing, the Design Assistant reduces irrelevant alerts for parts of the design that already meet timing requirements.