This real-time operating system only supports the RL78 family C compiler package. It does not support the RL78, 78K family C compiler package.


This product is a real-time operating system (Real-time OS) conforming to the μITRON4.0 Specification, the predominant Real-time OS for embedded systems in Japan. Its compact resources, outstanding real-time features, and many service calls are suited for an embedded system with real-time ability and multi-tasking functions. In addition, its affinity for the IDE CS+ and the configurator which automatically generates startup files will help you greatly reduce development time and get to market faster.

*TRON Forum holds the copyright on the μITRON Specification.

*TRON, ITRON, and μITRON do not refer to any specific product or products.

Release Information


Latest Ver.: V2.00.00

Released: Jun 1, 2015

Details of upgrade (See Tool News)

Operating Environment

Agreement Details

 User's Manual( Coding | All )

CS+ interface plug-ins (Real-time OS Common plug-in)

Latest Ver.: V3.03.00

Released: Jul 1, 2016

CS+ interface plug-ins (Plug-in for RI78V4 V2)

Latest Ver.: V2.01.00

Released: Jul 1, 2016

Cooperating Tools

  • Supported compiler :CC-RL
  • Supported IDE :CS+


  • Conforms to µITRON4.0 Specification:
    The design conforms to the µITRON4.0 Specification, the representative OS architecture for embedded control.
  • Achieving higher performance
    The times for processing service calls and the longest times over which interrupts must be disabled are shorter than for the RI78V4 V1.
    Service call processing time Difference from the RI78V4 V1
    Average (usec) Percentage
    Comparison in non-trace mode Shorter by 10.66 us 37.86% faster
    Longest time over which interrupts must be disabled Difference from the RI78V4 V1
    Average (usec) Percentage
    Comparison in non-trace mode Shorter by 9.27 us 44.00% faster
  • Excellent portability:
    In order to support many execution environments, the hardware-dependent processing necessary for the RI78V4 to execute processes has been extracted as target-dependent and user own coding portions and is provided as sample source files. In this way, portability to many different execution environments has been improved and customization is easy.
  • ROM-based implementation:
    Since the system is a real-time/multi-tasking OS assumed to be used embedded in the execution environment, it was designed to be compact and ready for ROM-based implementations. Also, because the system can be configured linking only the service calls used in the system by the user (rather than all the service calls provided by the RI78V4), a real-time/multi-tasking OS can be configured which is compact and optimized for the user's needs.
  • Interface with CS+, the Renesas Electronics Integrated Development Environment
    The RI78V4 OS interfaces with CS+ to support the following functions:
    • Auto-settings for options required in OS build
    • Displays state of OS control object for tasks, semaphore, etc (Resource Information)
    • Graphical displays of task operation history and service call issuance history (Task Analyzer)

    CS+ (Resource Information)

    CS+ (Task Analyzer)


The RI78V4 kernel consists of the following modules. Each module is provided by functions (service calls) .

  • Task management functions
    The task control functions provided by the RI78V4 include a function to reference task statuses, in addition to a function to manipulate task statuses.
  • Task dependent synchronization functions
    Changes task status from other task, and synchronizes tasks.
  • Synchronization and communication functions
    The synchronization and communication functions of the RI78V4 consist of Semaphores, Eventflags, Data Queues, and Mailboxes that are provided as means for realizing exclusive control, queuing, and communication among tasks.
    • Semaphores: In the RI78V4, non-negative number counting semaphores are provided as a means (exclusive control function) for preventing contention for limited resources (hardware devices, library function, etc.) arising from the required conditions of simultaneously running tasks.
    • Eventflags: Provides 16-bit eventflags as a queuing function for tasks, such as keeping the tasks waiting for execution, until the results of the execution of a given processing program are output.
    • Data Queues: Provides the data queues that have the data queue area in which data read/write is enabled for transferring the prescribed size of data.
    • Mailboxes: Provides a mailbox, as a communication function between tasks, that hands over the execution result of a given processing program to another processing program.
  • Fixed-sized memory pool
    When a dynamic memory manipulation request is issued from a processing program in the RI78V4, the fixed-sized memory pool is provided as a usable memory area.
  • Time management functions
    The time management functions of the RI78V4 include Delayed Wakeup, Timeout, and Cyclic Handlers that use timer interrupts created as fixed intervals, as means for realizing time-dependent processing.
  • System state management functions
    For changing or referencing the system state.
  • Interrupt management functions
    Provides as interrupt management functions related to the interrupt handlers activated when a maskable interrupt is occurred.
  • System configuration management functions
    Provides system initialization processing, which is required from the reset interrupt output until control is passed to the task, and version information referencing processing.
  • Scheduler
    The scheduling functions provided by the RI78V4 consist of functions manage/decide the order in which tasks are executed by monitoring the transition states of dynamically changing tasks, so that the CPU use right is given to the optimum task.


Target device RL78 Family
Maximum number of tasks 127
Number of priority levels 15
Number of Service calls 76
Performance (Time takes for a target task to be executed after the wup_tsk is issued.) 11.80 microseconds
(RL78/G13, 10MHz. non-trace mode)
Kernel code size From 3.0K bytes to 9.0K bytes
Kernel RAM usage per task data : 24 bytes
stack : 20 bytes + amount being used by the user


Provided items Explanation Note
Kernel source program Source files for the kernel Provided only with mass- production licenses which include source code.
Kernel library Kernel library for system building -
Standard header files
  • ITRON specification common definition files
  • Kernel specification definition files
  • Other definition files
Header files are provided in C language.
Command line configurator Outputs all types of definition files from the cfg file that describes the structure parameters in text. -
Sample program A simple program using ITRON. -
CS+ interface plug-ins
  • Real-time OS Common plug-in
  • Plug-in for RI78V4
  • Function for easy kernel embedding
  • Function for referencing the OS state during debug
  • A tool that displays a transition diagram of the OS operation history and analyzes performance, such as CPU usage rate.
Manual User's manual -

Processing Flow

About Trial

We provide a trial software of the RI78V4 so that you can try out the functions and performance of RI78V4 before purchasing it. No support, including responses to inquiries through contact points, is provided for the trial software. Please accept this before using the trial software. In addition, please read through the  Software User License Agreement and following notes before downloading.

Before Downloading

Cautionary Notes

  1. Difference with the Product Version
    Although the performance and functionality are the same as the product version, RI78V4 real-time OS of the trial software has the restrictions described below.
    • The RI78V4 OS stops working after 30 minutes (the program enters an infinite loop).
  2. Using the OS for Finished Products
    If you intend to embed the RI78V4 real-time OS in a finished product, use the product version. We do not offer any technical support services in case of troubles.
  3. Prohibition of Redistribution
    Redistribution of the software tool to third parties is strictly prohibited.

Operating Environment

The operating environment is same as the product version. Refer to Operating Environments of Products.


Devices with exceedingly low ROM or RAM capacity are not supported even if the groups they belong to are listed on the above list of supported devices. The standard capacities of ROM and RAM are stated below. Note that the required capacities also depend on the applications you will be using.

  • ROM capacity: At least 16 KB
  • RAM capacity: At least 4 KB

Information supporting development tools

Title Description
My Renesas Create a My Renesas account to use our tool download services,
receive e-newsletter/update notifications, and take advantage of our other services.
e-learning Information for studying and learning about microcontrollers and microprocessors.
FAQ Frequently asked questions and useful hints for development.
Forum A forum and community site to share technical information,
questions and opinions with others who use Renesas MCU's.
Tool News Tool release information and other important information.
Operating Environment Information on system requirements and operating environment for the latest
version of tools.
Info on Discontinued Products A list of Renesas software and tools that have been discontinued and
are no longer being offered for new projects.