Start Your Engines: Win Le Mans with the SimVision Mixed-Signal Debug Option

12 Mar 2021 • 5 minute read

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Cadence^® Spectre^® AMS Designer is a high-performance mixed-signal simulation system. The ability to use multiple engines and drive from a variety of platforms enables you to "rev up" your mixed-signal design verification and take the checkered flag in the race to the market. The Start Your Engines! blog series will provide you with tips and insights to help you tune up your simulation performance and accelerate down the road to productivity.

Bonjour!

In this post, I will explain how the new Cadence SimVision Mixed-Signal Debug (SimVision MS) option can reveal the Invisible portions of Analog and Mixed-Signal Test Benches (TB).

In your daily work with AMS Designer, you may have some complex goals to achieve when setting up and running a SoC mixed-signal verification. These would be to check the operation of the circuit in the electrical as well as digital context and see what happens in between. In addition, it is essential to complete the tasks in a limited time window. Mixed-signal (MS) debugging can seem a lot like driving at the Le Mans race, a grueling 24-hours endurance test! Such a long race may not seem grueling if you end up winning. Similarly, SimVision MS will give you a winning experience with AMS debugging. Let me guide you how.

Studying Connect Modules Insertion and Operation

When you run a MS simulation, the simulator executes three steps:

Compiles the models
Then, elaborates the TB simulation snapshot
Finally, simulates the TB

When two ports of different types (electrical, logic, or real) are connected on a net, a connect module (CM) is automatically inserted at the end of the elaboration process. This connect module contains the code required to translate and propagate signals between the two ports. CM parameters’ setup is an important task for the engineer in charge of MS simulation because it is necessary for MS simulation accuracy and speed performance.

Mixed Nets Browser

SimVision MS provides a new tool named "Mixed Nets Browser". It lists all the mixed nets in the TB and automatically inserts CM instances. The CMs are displayed in a table. This table (Figure 1) allows you to compare the CMs and profiles the CMs based on their A2D/D2A activity, X state generation, or electrical overvoltage. You can customize this table with custom variables. Then, you can send a CM instance to the source debugger for a step-by-step investigation. The GUI lets you create an effective mixed-net schematic with ease. The diagram could represent the port (electrical, logic, or real) connections through all the hierarchy levels.

Figure 1: Mixed Nets Browser with E2L and L2E Connect Modules Instances

Electrical Currents Invisibility

By default, a SPICE electrical solver does not compute the currents unless you probe them, and the port currents are invisible. SimVision MS provides you an innovative way to select an electrical net in Schematic Tracer (Figure 2) and monitor the current flow values of all the ports on local scope or through the hierarchy. You have access to the electrical currents’ distribution. In addition, the graphical user interface lets you sort the currents and you can cross-select using Schematic Tracer. The beauty of this current distribution browser is that it does not require any proactive current probes to be set up. Therefore, you can avoid transient simulation slowdown caused by currents probes.

You could also use the current distribution on a net for:

A smart and powerful electrical connectivity analysis
An immediate answer for currents leakage investigation on local scope or through subcircuits hierarchy

Figure 2: Node Currents Distribution in a Local Scope

Virtuoso^® Schematic Editor <=> Simvision Debugger Cross-Selection

The bidirectional cross-selection feature helps the designer with many tasks during the MS Debug process. Instead of going through two separate time-consuming searches: one in the Virtuoso Schematic Editor and another in the SimVision tools; the cross-selection feature allows the designer to find a specific instance, group of parts, or a net from Schematic Editor and view it as highlighted in Schematic Tracer.

With cross-selection, the same part is selected within the SimVision tools as well, such as Design Browser, Schematic Tracer, and Waveform (if this node was already plotted). If you change the hierarchical-level scope object selection in SimVision, Schematic Editor will auto-focus the selection on the same hierarchical-level scope.

Key Benefits of Using SimVision MS

Access to Mixed Net Browser, a superior and interactive analysis tool
Electrical context and mixed net schematic creation
Connect module profiling
Connect module source debugger
Access to invisible electrical currents distribution on a node
Easier Leakage current study
Bidirectional cross-selection between Virtuoso Schematic Editor and SimVision tools

We have received excellent feedback from the designers who have started using the SimVision MS debug option. Quoting feedback from one of the designers “These are great features for debugging MS design. I became a hero at debugging my design and in the MS Verification Team.”

There are more than twenty new features in SimVision MS. This tool is easy to learn and use. You can use it for many different types of circuits. Connect to the Cadence Support portal to discover more.

With the new features of SimVision MS, you will be the trophy winner in the field of AMS SoC verification. I wish you a winning experience.

~ Andre Baguenier

Related Resources

For more information on Cadence circuit design products and services, visit www.cadence.com.

About Start Your Engines

The Start Your Engines! series brings you blog posts from several analog/mixed-signal subject matter experts on a variety of topics, such as introduction to the new features in Spectre AMS Designer, tips for enhanced understanding of existing features, and much more. To receive notifications about new blogs in this series, click Subscribe and submit your email ID in the Subscriptions box.