Renesas Electronics Announces Development of Virtualization Technology Suitable for Real-Time Processing of V850 CPU Core

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12 Oct 2010

TOKYO, October 12, 2010 — Renesas Electronics Corporation (TSE: 6723), a premier supplier of advanced semiconductor solutions, today announced the development of virtualization technology for the V850 CPU architecture that assigns an appropriate amount of CPU time to each process and dramatically reduces interference between control processes in control systems that perform high-speed and composite processing of diverse tasks. The new virtualization technology allows for increased software configuration freedom when running on a single CPU core, particularly in large-scale control systems that perform composite processing, and enables smooth distribution and integration of functions for more efficient software development.

Recently, there has been a rapid shift to electronic control systems in applications such as automotive control units where high-speed and complex real-time processing is required. In addition, the number of control systems per vehicle has increased. As such systems proliferate, there are cases where control systems have to be changed to provide distribution and integration of functions, as well as cases where, because individual control systems have become larger in scale as existing functions become more sophisticated and advanced, functions have been divided among multiple interoperating control systems in order to simplify the design process. In addition, there are cases where the application software has been divided up into modules to restrict access to memory (ROM, RAM, peripheral devices) or enable execution management to enhance the safety and reliability of the control systems overall in response to functional safety standards such as SIL* or the requirements of the security field.

In such cases in the past, software was used to divide or integrate functions, or multiple hardware units (CPU cores) were used, with one assigned to each individual control system. However, software-based integration is not well suited to real-time control applications because extra CPU processing time is needed for tasks such as time management and program switching. The use of multiple hardware units is also problematic because the number of control systems will sometimes increase during the software development process, making it difficult to procure the optimum hardware ahead of time.

For this reason, there is a need for a development environment that minimizes interference among multiple control systems, maintains independence of process execution, and simplifies quality assurance while also allowing flexible software reconfiguration to accommodate changes during the software development process and parallel development of multiple derivative products.

Furthermore, there is a trend toward software development that envisages parallel operation from the initial stage as demand grows for multicore hardware aimed at reducing power consumption and boosting operation performance. To ensure scalability, software must be hardware-independent. There is growing demand for hardware that allows the level of parallel processing to be changed flexibly, both to enable the parallelism demanded of application software and because the necessary degree of parallel processing can differ from that assumed when the hardware was initially chosen.

As a solution to these issues, Renesas Electronics has developed virtualization technology that allows parallel execution without mutual interference among multiple system control tasks on a single CPU.

The main functions of the newly developed technology are as follows.


  • (1) Hardware scheduler supporting parallel execution of multiple real-time control tasks

    Renesas Electronics has developed multithreading technology that enables multiple threads to execute in parallel. It enables each thread, or unit of software execution, to have multiple resources needed for program execution, such as general registers and system control registers, and switches among the running threads each clock cycle.


    Thread switching is handled automatically by a hardware scheduler, ensuring that each thread is provided with the CPU time assigned beforehand by the developer. This eliminates the need to devote CPU processing time to time management and program switching, which was indispensable previously. Regularity is maintained and multiple real-time control systems can run in parallel with frequency performance meeting requirements specified by the developer.


  • (2) Ability to configure a single CPU as multiple virtual CPUs

    Renesas has developed hardware that extends the way address space and interrupt handling are managed, making it possible to configure a single CPU as multiple virtual CPUs.


    An address conversion function provides appropriate separation of memory resources such as application software code areas and data areas, preventing overlap of logical addresses among virtual CPUs or misallocation of memory resources. It is also possible to manage interrupt priority independently for each virtual CPU.


    Each virtual CPU may be assigned either single or multiple threads. With a simple OS such as a real-time OS, a single thread can be assigned to each virtual CPU. When running a large-scale OS with support for multithreading, multiple threads can be assigned to a single virtual CPU.


  • (3) Bus system that reduces interference between threads

    The bus system minimizes interference between threads accessing memory (ROM, RAM) connected to the bus or the main peripheral devices and maintains the regularity of input/output (I/O) access by the various threads. This provides support for I/O virtualization in control systems.


By combining these features, the new technology makes it possible to use a single CPU as multiple virtual CPUs and individual virtual CPUs can each run a different OS or support independent control systems running in parallel.


The new technology can also solve software overhead problems related to time management that can occur when dividing or integrating multiple control systems or, during development of large-scale control systems, when granular time control is disrupted when changing and verifying individual control systems or before and after integration. This makes it possible to divide or integrate multiple control systems at optimal cost. In addition, there is more freedom regarding the number of virtual CPUs and the combination of frequency performance levels in a virtual multi-core configuration. This means the design process can take into account board characteristics such as mounting location and mounting area.


Renesas Electronics plans to implement the newly developed virtualization technology in its next-generation V850 CPUs to provide a new level of CPU architecture scalability and contribute to more flexible development systems for customers.


(Note 1) Safety Integrity Level
A level of safety stipulated in the functional safety standard for electronic products (IEC 61508) and the functional safety standard for road vehicles (ISO 26262).

About Renesas Electronics Corporation

Renesas Electronics Corporation (TSE: 6723) delivers trusted embedded design innovation with complete semiconductor solutions that enable billions of connected, intelligent devices to enhance the way people work and live. A global leader in microcontrollers, analog, power, and SoC products, Renesas provides comprehensive solutions for a broad range of automotive, industrial, home electronics, office automation, and information communication technology applications that help shape a limitless future. Learn more at

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