Mixed-Signal Design Blogs

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.

Hello AMS Engineers,

In this post, I will explain how easily you can now debug Interface Elements (IE) or Connect Modules (CM) using SimVision MS.

When you run a mixed-signal simulation, the simulator performs three steps:

1. Compiles the models
2. Elaborates on the testbench simulation snapshot
3. Simulates the testbench

When two ports of different types: electrical, logic, or real, are connected to a net, an IE or CM is automatically inserted at the end of the elaboration process. Each IE contains the code required to translate and propagate signals between two ports from different disciplines. Setup of IE parameters is an important task necessary for the accuracy and performance of a mixed-signal simulation. In this blog, I will introduce you to the amazing features of SimVision MS that help you set up and debug IEs for a mixed-signal simulation.

Before that, I would like to share an interesting fact—Interface Elements or Connect Modules are the same types of objects. Interface Elements is the original name used by Cadence since the nineties. Several years later, the Verilog-AMS Language Reference manual started naming these objects as Connect Modules. Maybe the IEEE SystemVerilog-AMS standardization group will rename these objects as "adapters" in the future.

Mixed Net Browser

The Mixed Net Browser tool in SimVision MS looks for all the mixed nets in a testbench and automatically displays the inserted IE instances. By switching the tabs in the Mixed Nets assistant, you can view the mixed nets as a list or in the design hierarchy tree. Names of the IEs or CMs are displayed in the Module column in the Mixed Net Browser window. You can also see the activity of each IE and monitor each internal parameter and variable value at the current time of simulation.

Mixed Net Browser displaying the IEs for an example testbench

In the Mixed Net Browser, you can select an IE instance and send it to the Source Browser to see the activities of the selected IE in detail.

Source Browser

The Source Browser provides a powerful capability to study the values of parameters in the Verilog-AMS or SystemVerilog-AMS behavioral code.

The Source Browser back annotating the behavioral code parameter values for the L2E interface element

You can also review the internal variable values at the current time of the simulation. For example, at any time during the simulation, you can identify the L2E Din driver, as shown in the figure below.

L2E Din driver identification at the current time in simulation

You can efficiently investigate the detailed operation of an IE instance and solve difficult AMS problems by using the various capabilities offered by the Source Browser. This browser lets you 

• Read the IE Verilog-AMS or SystemVerilog-AMS behavioral code with annotated values of the parameter and variables at the current time of simulation
• Set up a breakpoint based on an event or a change in value
• Identify the drivers or loads
• Create a mixed-net schematic out of the box

A mixed-signal net schematic created by Source Browser. The digital object instances are in green and the MOS and analog block instances are in red. The IE instance anchor point is represented by a diamond.

We have been receiving excellent feedback from the designers who are already using these powerful tools of SimVision MS.

I would like to quote two here:

User 1: “I became in my AMS design team a Hero of Mixed Signal Verification. “

User 2: “SimVision MS reveals the invisible. It becomes easy to overcome difficult problem of Connect Modules wrong user setup and unexpected operation in my TB.”

Hope you are now excited to try out these useful features yourself. If you need more details, contact your Cadence Support team.

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

Andre Baguenier

Contact Us

For any questions, general feedback, or even if you want to suggest a future blog topic, write to custom_ic_blogs@cadence.com.

About Start Your Engines

The Start Your Engines series would bring you blog posts from several analog/mixed-signal subject matter experts on a variety of topics, such as an introduction to the new features in AMS Designer, tips for enhanced working with 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.