Arasan Establishes Mixed Mode Simulation with Pyxis SchematicArasan Chip Systems is a leading provider of Total IP solutions for mobile storage and connectivity applications.
“The response from the digital engineer who is using it has been very positive...It’s relatively simple and transparent to him. I’ve used Pyxis and I’m sure we’re going to be using it more and more because we have to develop a greater level of analog/digital and mixed signal capability as time goes on and because Pyxis vital for the quality and accuracy of our designs.”
product overview: Pyxis Schematic, part of Mentor's Pyxis Custom IC Design Platform, provides a powerful and easy-to-use design entry environment with advanced capabilities that boost designer productivity.
Founded in 1995, Arasan Chip Systems is a leading provider of Total IP solutions for mobile storage and connectivity applications. Arasan’s Total IP solutions provide silicon-proven, validated IP delivered with the ability to integrate and verify both digital, analog, and software components in the shortest possible time with the lowest risk.
In the design of a D-PHY communications circuit, using the MIPI mobile interface PHY standard, Arasan needed an analog mixed-signal solution that could handle a high level of mixed signal complexity, different levels of design abstraction, and support multiple CAD tools in an integrated, unified environment. They also needed the tool to perform speed and power optimizations at both the architectural and cell levels.
Designed for use by Arasan customers in a variety of architectures, the D-PHY circuit provides fast data transfers between different devices without using a lot of power, converting serial I/O information to parallel. Because it features a complete set of analog functions and a full level of logic circuits that have to interface with the analog circuits, the design required a major effort on both sides of the design team. The large amount of combined digital and analog promised a difficult and significant effort.
Because of their long experience using several Mentor solutions, such as ModelSim, Eldo, and Questa ADMS, they trusted the quality of its tools and the expertise and dedication of its support staff. For these reasons as well as the merits of the tool itself, they decided that Pyxis Schematic was the best tool to meet these significant challenges.
Superlative Support for a New Flow
In order to adopt Pyxis Schematic, they had to convert the MIPI DPHY schematics and supporting libraries into the Pyxis environment. Christopher Arcus, Principal Analog Design Engineer at Arasan, headed up this effort.
“Pyxis Schematic was the gateway solution for us to be able to work with multiple vendor tools and do a mixed signal simulation in a Mentor environment with the Pyxis tools, which I think is a superior approach to doing mixed signal simulation,” Mr. Arcus avers. “The Mentor tools have been designed from a design engineer’s perspective; they feel like they make sense relative to the task that you’re trying to achieve.”
Still, the initial set up and conversion to Pyxis Schematic was a major effort. Arasan is interested in this solution because all of their functions are mixed analog/digital, and they have to support all their customers, and do it in multiple CAD vendor tool environments. “So we have these levels of difficulty,” says Mr. Arcus, “and given the fact that we’re doing this with different tool vendors and with different customers and analog and digital, it’s vital that we have support for that kind of effort.”
Thus, one of the main reasons they chose Pyxis was because of the known level of support they would receive from Mentor.
“My job was to get the tool running,” Mr. Arcus says. “I was able to do this because of the support. We had already been using some Mentor tools, and we were getting good support. And that only continued and got better. I’ve had access to multiple, very skilled Mentor personnel within the company on this project. We’re using some of the most advanced tools, and some of the most up-to-date versions of the software, and if we have an issue to deal with, Mentor finds a solution to it very quickly. Compared with other vendors, there is no comparison.”
Multiple Perspectives on Mixed Signals
The Arasan team needed to track the relationship between what was going on in the lab and what was going on in simulation. Their primary area of interest was the interface between the analog and digital parts of the design.
Without full mixed signal simulation, they could exercise some behavior on the HDL side, using an equivalent circuit to model what is happening in the analog side. However, an equivalent circuit cannot accurately model the signals going back and forth between digital and analog, so the simulation environment fails to pick up all of the behavior. What they needed to be able to do was simulate the digital behavior along with the entire analog circuit. One way to do this is to use a text-based solution to replace the equivalent circuit with a netlist, running the analog underneath the digital. This yields accurate and useful results on the digital side, but it does not allow designers to match up a result on the digital side with a node on the analog side to understand what’s going on.
Pyxis solves this problem by using a schematic to give the desired level of insight and enable the necessary correlations between the analog and digital domains.
“Mentor has recognized that you need to look at the simulation results from different viewpoints,” Mr. Arcus reports. “One is more from the digital side, and the other is more from the analog side. This is very useful. Being able to have schematics in the Pyxis environment and run Eldo on it, allows us to track all the relationships of signals and variables and compare them.”
Another advantage of Pyxis Schematic is that it provides a framework for mapping and understanding the signal flow. It provides a complete, top-level concept of how the architecture works.
“It’s one set of schematics that you use to look at everything,” Mr. Arcus reports. “You see the interaction in terms of the pins, and you see the blocks themselves. So it helps from an architectural standpoint to see what’s going on.”
Unified Flow Boosts Quality and Productivity
Having a single set of schematics for both the digital and analog groups working on the project is beneficial for design and development. A unified environment eliminates the pin mismatches and resultant signal incoherency that often occur when digital and analog development is done separately. It also allows both top-down and bottom-up design.
“Pyxis enables system-level designers to get all the detail between the top-level analog and digital squared away, so that the digital and analog teams can go off on their own and develop all the other parts because they are secure in the fact that the top-level has already been established and functions correctly,” Mr. Arcus explains. “Pyxis gives you a coherency to the design that you might otherwise not have, which impacts both design quality and productivity.”
Putting all of this capability in a single tool environment can get messy. But the Pyxis platform is as integrated and unified as the flow it enables.
“The Pyxis Schematic environment is set up to be a fully integrated tool environment,” observes Mr. Arcus. “There’s a lot in there; everything from the different simulators that you can go to from both the analog and the digital side to the way it deals with different abstraction levels and models for each individual cell. The GUI makes all of this easy to deal with. It has multiple yet consistent ways of viewing things. The more that the tools, the environment, and the interfaces are consistent across everything; the easier it is to use them. This is not consistent across the industry. Not everyone pays attention to the user interface, and that makes a difference in efficiency.”
It is also easy to use Pyxis in these many tool and design environments. “Another beautiful thing about the Pyxis tool environment is that it’s totally transportable,” Mr. Arcus continues. “You just have it set up so that, no matter where you are, no matter what you do with the tool, you place it with the configuration files and it knows where everything is, and you don’t mess with them either. It’s pretty much transparent to you.”
A Successful Introduction
Now that Pyxis is fully adopted, Arasan has a capability that they did not have previously, and the story is ongoing.
“Mentor has recognized that you need to look at the simulation results from different viewpoints....One is more from the digital side, and the other is more from the analog side. This is very useful. Being able to have schematics in the Pyxis environment and run Eldo on it, allows us to track all the relationships of signals and variables and compare them.”
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