This product is a real-time operating system (RTOS) conforming to the μITRON 4.0-specification, the predominant RTOS 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+ will help you greatly reduce development time and get to market faster.

This product is different from the V2.00.xx series of RI850V4 real-time operating systems for the RH850 family of MCUs.

  • TRON Forum holds the copyright on the μITRON Specification.
  • TRON, ITRON, and μITRON do not refer to any specific product or products.

Release Information

Details of upgrade (See Tool News)

Operating Environment

Agreement Details


Latest Ver.: V1.01.00

Released: Oct 1, 2014

CS+ interface plug-ins (RTOS Common plug-in)

Latest Ver.: V3.00.00

Released: Oct 1, 2014

CS+ interface plug-ins (Plug-in for RI850V4 V1)

Latest Ver.: V3.00.00

Released: Oct 1, 2014


  • Conforms to µITRON Ver. 4.0 Specification:
    The design conforms to the µITRON Ver. 4.0 Specification, the representative OS architecture for embedded control, providing all functions specified as standard profile, and it provides extended synchronization and communications functions (mutexes) and memory pool management (variable-sized memory pools) as extended functions.
  • Excellent portability:
    To support various execution environments, the RI850V4 extracts hardware-dependent processing that is required to execute processing as user-own coding modules and target-dependent modules, and provides it as sample source files. This enhances portability for various execution environments and facilitates customization as well.
  • ROM-based implementation:
    Since the system is a real-time/multitask 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 application system by the user (rather than all the service calls provided by the RI850V4), a real-time/multitask OS can be configured which is compact and optimized for the user's needs.
  • Realization of memory savings:
    By using functions provided by the RI850V4, such as restricted tasks and preempt disable, the system's memory consumption can be reduced.
  • Interface with CS+, the Renesas Electronics Integrated Development Environment
    The RI850V4 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)
    • Generates service calls to start up tasks from debugger, set up event flags, etc.
    • Graphical displays of task operation history and service call issuance history (system performance analyzer)
  • Interface with "MULTI" Integrated Development Environment from Green Hills Software.
    The RI850V4 OS interfaces with MULTI to support the following functions:
    • Displays state of OS control object for tasks and semaphore, etc. (task, debugger)
    • Graphical displays of task operation history and service call issuance history (system performance analyzer)


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 generation, activation and termination of tasks.
  • Task dependent synchronization functions
    Changes task status from other task, and synchronizes tasks.
  • Task exception handling functions
    The task exception handling functions of the RI850V4 include a function related to the task exception handling routine that is activated when a task exception handling request is issued (function for manipulating or referencing the task exception handling routine status).
  • 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.
    • Mutexes: Provides a mutex, as a function to prevent contentions on using the resources.
  • 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 sych 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.




Target device V850
Maximum number of tasks 255
Number of priority levels 32
Service call number 132
(Time takes for a target task
to be executed after the wup_tas is issued.)
16 microseconds
(V850E/MA1, 25MHz. embedded memory)
Kernel code size From 6K bytes to 20K bytes
Kernel RAM usage per task data : 32 bytes
stack : 128 bytes




Provided items Explanation Note
Kernel source program Kernel source program 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 both in C languages
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
- RTOS Common plug-in
- Plug-in for RI850V4
Function for easy kernel embedding
Function for referencing the OS state during debug
System performance analyzer A tool that displays a transition diagram of the OS operation history and analyzes performance, such as CPU usage rate. Interfaces with CS+ and MULTI
Task debugger A tool for referencing the OS state during debug Interfaces with MULTI
Manual User's manual  



Processing Flow

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