Atmel and the use of Verilator to create uc Device Models

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1 Atmel and the use of Verilator to create uc Device Models Dag Braend Sr Director Atmel MCU Tools Roland Kruse Jie Xu Jan Egil Ruud Atmel Co-simulation Team Copyright Atmel Corporation 14/Jan/2013

2 Background Atmel is a major provider of 8 and 32 bit MCU solutions AVR proprietary architecture for consumer and industrial 8 bit devices ARM Cortex M4 architecture for consumer and industrial 32 bit devices maxtouch proprietary architecture for capacitive display touch applications Atmel specializes in picopower technologies latest offering is the lowest power ARM Cortex M4 based device SAM4L Atmel MCU Tools is the primary marketing channel for our devices Atmel Studio Complete Integrated Development Platform Atmel Gallery Atmel and 3rd party functional extensions Atmel Spaces Collaborative workspace with Atmel Studio integration Copyright Atmel Corporation 14/Jan/2013

3 Simulator Atmel uses MCU simulators as a debugging tool for customers doing application development We currently do NOT use simulators as a way to validate the IC development We do NOT use simulators in a systems simulations fashion (why? They are too slow) We use simulators as a target where the customers can validate their C/C++ MCU code before they deploy the code on an actual HW target Simulators are integrated as targets in the Atmel Studio IDE The IDE does not see the difference between a simulated target and an actual HW target they should behave the same For this scenario to work we need Cycle accurate simulation of the complete device, including different memory types and analog front-ends. Only way to do this is to re-use the code for the actual device when making the simulator model Atmel currently sells > 350 uc models. We need a simulator model for each. Thus the model creation process is extremely important Copyright Atmel Corporation 14/Jan/2013

4 Simulators - History Atmel has worked with creating simulator models for many years and has employed different tool chains for the job VTOC Carbon Design Systems The use of commercial tool chains has proven difficult This is a complex and specialized field with not so many customers = expensive tools The companies that support the tools tend to be small = will support their major key customer at any given time but if you are not the largest you suffer Some of the providers have business models and license agreements that does not fit well with free distribution of unlimited number of licenses Some of the providers have business models that makes Atmel a competitor of the company providing the technology Conclusion: Atmel wanted to explore the use of open source tools for this development Copyright Atmel Corporation 14/Jan/2013

5 Main advantages of working with open source tools No license fees. What we pay goes into real work, either development of new features, or real support. If we choose to not pay for these services anymore, we still have the tools. Tools will always be available, no matter what happens to the project. Both our earlier changes of tools were enforced by non-technical issues with the companies owning the tools. No concerns with software license management Atmel can deploy the tool chain at multiple design locations without difficult license negotiations We benefit from work contributed by others, at no additional cost. Source code access Having the source code of the tool is very helpful when problems occur, or when we create in-house tools to support our workflow. Reduced bug fixing cycle time The open source model have the potential of drastically shortens the cycle when bugs are fixed, we don t have to wait until the vendor produces a new version (if ever). But it requires an active community and a certain level of use Copyright Atmel Corporation Jan

6 The psychology of SW purchases Companies (read Atmel) are less willing to buy expensive SW SW license management is always a hassle and multinational companies like Atmel don t like it when you start talking of site licenses, licenses located to geographies, encounter different pricing schemes in different regions Companies are however willing to pay consultant fees in order to have required SW modifications done An open source model where companies (like Atmel) Copyright Atmel Corporation Select Insert > Header & Footer > Type Title in Footer field 06/10/2012

7 Simulator Atmel and Verilator Atmel has visited the Verilator project on several occasions over the years and previously the feel was that the tool was immature and would not fit Atmel s needs. Atmel revisited the tool in 2011 and found that the situation had changed the tool seemed much improved In 2012 Atmel engaged with Embecosm in order to make Verilator support the required Atmel device implementation and development flow. There has been a number of technical issues to be resolved, and in addition Embecosm has implemented System Verilog support. The experience with getting Verilator to work has been comparable to the commercial tools there is no out of the box experience to be had in this respect Copyright Atmel Corporation Select Insert > Header & Footer > Type Title in Footer field 06/10/2012

8 Verilator work flow Simplified view of the simulator model architecture Copyright Atmel Corporation Jan

9 Verilator work flow Main steps of model creation Replace top level module. Remove non-synthesizable parts of the hierarchy. Adapt top level I/O ports to fit C++ wrapper. Create replacements for modules that cannot be used with Verilator. This includes NVM, UDPs, etc. Make the design compile with Verilator. This may require minor changes in RTL code throughout the hierarchy. Create DPI functions to access memories, CPU registers, and I/O from C++ code. This process is partially based on machine-generating Verilog and C++ code from an XML description. Write the device-dependent part of the C++ wrapper. This part is responsible for driving the model (reset, clocks, etc). Test the completed model. Set up for production build. This includes creation of the Windows version of the model (cross-compiled on Linux) The model is tied to Atmel Studio with a small XML file (binding device name to DLL file name) Copyright Atmel Corporation Jan

10 2012 Atmel Corporation. All rights reserved. Atmel, Atmel logo and combinations thereof, Enabling Unlimited Possibilities, and others are registered trademarks or trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be trademarks of others. Disclaimer: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN THE ATMEL TERMS AND CONDITIONS OF SALES LOCATED ON THE ATMEL WEBSITE, ATMEL ASSUMES NO LIABILITY WHATSOEVER AND DISCLAIMS ANY EXPRESS, IMPLIED OR STATUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE, SPECIAL OR INCIDENTAL DAMAGES (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS AND PROFITS, BUSINESS INTERRUPTION, OR LOSS OF INFORMATION) ARISING OUT OF THE USE OR INABILITY TO USE THIS DOCUMENT, EVEN IF ATMEL HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. Atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifications and products descriptions at any time without notice. Atmel does not make any commitment to update the information contained herein. Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications. Atmel products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life Copyright Atmel Corporation 14/Jan/2013