This product is a real-time operating system (real-time OS) that is an implementation of the μITRON4.0 specification. μITRON is the predominant real-time OS for embedded systems in Japan. Its low resource requirements, outstanding real-time performance, and broad range of service calls make it very suitable for embedded systems requiring true real-time and multi-tasking capabilities.

In addition, its high degree of compatibility with the CS+ IDE and the configurator which automatically generates startup files will help you greatly reduce development times and get your products to market more quickly.

This product is also available in the free trial version.

Important:RI850V4 V2 is not a multicore OS. However, while it does not support multicore OS functionality, it can be run at the same time on each of the cores of a multicore MCU.

Important:This product is a separate product from RI850V4 V1.00.xx.



  • Conformance with the µITRON4.0 Specification
    The design conforms with the µITRON4.0 Specification, which prescribes a representative OS architecture for embedded control.
  • Excellent portability
    To support its execution in various environments, the RI850V4 is separated into the target-dependent section for hardware-dependent processing and the parts for use in the user’s own code. Sample files of source code are provided. This enhances portability to various execution environments and facilitates customization.
  • ROM-based implementation
    Since the system is a real-time and multi-tasking OS designed on the assumption of usage in embedded execution environments, it was designed to be compact and ready for ROM-based implementation. A system can be configured with only those service calls that are actually used in the user’s application being linked (rather than all service calls provided by the RI850V4), so a real-time/multi-tasking OS which is optimally compact in terms of the user's needs can be configured.
  • Realization of memory savings
    The ability to disable preemption provided by the RI850V4 can reduce a system's memory requirements.
  • Interlinking with the CS+ Integrated Development Environment from Renesas Electronics[Learn More]
    • Automatic settings for options required in building the OS
    • Displaying the states of OS control objects such as tasks, semaphores, etc. (Resource Information)
    • Graphical display of the history of task operations and of issuing service calls(Task Analyzer. For the RH850G3MH core products, only software trace mode is available.)
  • Support by the MULTI integrated development environment from Green Hills Software, Inc.[Learn More]
  • Supported compiler: CC-RH, GHS
  • Learn More

Release Information


Latest Ver.: V2.01.01
Released: Jun 1, 2016
Details of upgrade (See Tool News)
Operating Environment
Agreement Details

User's Manual ( Coding: RI850V4 V2 Real-Time Operating System User's Manual: Coding (PDF | English, 日本語) | 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 RI850V4 V2)

Latest Ver.: V2.02.00
Released: Jul 1, 2016

Target Devices

Contact us if you are considering purchasing this product for use with a device of the RH850/P1x-C or RH850/P1M-E group.


Type Title Date
Upgrade - OS Log in to Download ZIP 17.12 MB 日本語
1 item


Additional Details

Cooperating Tools

  • Supported compiler: CC-RH, GHS 1
  • Supported IDE: CS+, MULTI 2
  1. GHS is a compiler package from Green Hills Software.
  2. MULTI is an IDE from Green Hills Software.


The RI850V4 kernel consists of the following modules. Each module is provided by functions (service calls) .

  • Task management functions
    Provided by the RI850V4 include a function to reference task statuses such as priorities and detailed task information, in addition to a function to manipulate task statuses such as creation, activation and termination of tasks.
  • Task dependent synchronization functions
    Changes task status from other task, and synchronizes tasks.
  • Task exception handling function
    Task exception handling function is unsupported.
  • Synchronization and communication functions
    The synchronization and communication functions of the RI850V4 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 RI850V4, 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 32-bit eventflags as a queuing function for tasks.
    • 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.
  • Extended synchronization and Communication functions
    Provides Mutexes as the extended synchronization and communication function for implementing exclusive control between tasks.
  • Fixed-Sized Memory Pools
    When a dynamic memory manipulation request is issued from a processing program in the RI850V4, the fixed-sized memory pool is provided as a usable memory area.
  • Variable-Sized Memory Pools
    When a dynamic memory manipulation request is issued from a processing program in the RI850V4, the variable-sized memory pool is provided as a usable memory area.
  • Time management functions
    Provides methods to implement time-related processing (Timer Operations: Delayed task wakeup, Timeout, Cyclic handlers) by using base clock timer interrupts that occur at constant intervals, as well as a function to manipulate and reference the system time.
  • System state management functions
    Provides functions for referencing the system status such as the context type and CPU lock status, as well as functions for manipulating the system status such as ready queue rotation, scheduler activation, or the like.
  • Interrupt management functions
    The RI850V4 provides as interrupt management functions related to the interrupt handlers activated when an interrupt (maskable interrupt, software interrupt, reset interrupt) is occurred.
  • Service call management functions
    Provides the function for manipulating the extended service call routine status, such as registering and calling of extended service call routines.
  • Scheduler
    The scheduling functions provided by the RI850V4 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.


Maximum number of tasks 255
Number of priority levels 32
Number of Service calls 118
Performance (Time takes for a target task to be executed after the wup_tsk is issued.) 4.75 microseconds (RH850E/F1L, in 80MHz equivalent, embedded memory)
Kernel code size 20K bytes 1
Kernel RAM usage per task data : 32 bytes
stack : 132 bytes
  1. The value is the maximum value in the case of using all service calls that provided by the RI850V4. It vary depending on the type of service call to be used.


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 RI850V4 V2
  • 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 -

Flow of Processing

Processing Flow

About Trial

We provide a trial software of the RI850V4 so that you can try out the functions and performance of RI850V4 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 ITRON (PDF | English, 日本語) 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, RI850V4 real-time OS of the trial software has the restrictions described below.
    • The RI850V4 V2 real-time OS stops operating after running for 60 minutes (the program enters an infinite loop).
    • The following service calls cannot be used.
      • set_tim
      • get_tim
  2. Using the OS for Finished Products
    If you intend to embed the RI850V4 real-time OS in a finished product, use the product version. We do not offer any technical support services in case of troubles by using trial software.
  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.


Please refer to RI850V4 Real-time OS for RH850 Family (Supported by CS+) Trial Software Further note (PDF | English, 日本語).