Version 13
    Ordering InformationKey FeaturesTechnical SpecificationsSupported DevicesVideoTechnical Documents






    µC/OS-II, the Real-Time Kernel, is a portable, ROMable, scalable, preemptive, real-time deterministic multitasking kernel for microprocessors, microcontrollers and DSPs. Offering unprecedented ease-of-use, µC/OS-II is delivered with complete source code and in-depth documentation. Most of µC/OS-II is written in highly portable ANSI C, with target processor specific code written in assembly language. Assembly language is kept to a minimum to make µC/OS-II easy to be ported to other processors. To date, µC/OS-II has been ported to over 40 different processor architectures, ranging from 8- to 64-bit CPUs. µC/OS-II can manage up to 250 application tasks and provides the services including: semaphores; event flags; mutual-exclusion semaphores that eliminate unbounded priority inversions; message mailboxes and queues; task, time and timer management, and more.


    μC/OS-II’s footprint can be scaled (between 5 Kbytes to 24 Kbytes) to only contain the features required for a specific application. Depending on the processor, μC/OS-II can be reduced to as little as 2K bytes of code space and 300 bytes of data space (excluding stacks). The execution time for most services provided by μC/OS-II is both constant and deterministic; execution times do not depend on the number of tasks running in the application.


    A validation suite has been developed for μC/OS-II and provides all the documentation necessary to prove that μC/OS-II is suitable for Safety Critical Systems common to Aviation and Medical products. Although this feature may not be applicable to your needs, it does prove that μC/OS-II is a very robust RTOS. μC/OS-II has been used in hundreds of products from companies all around the world. Specifically, μC/OS-II is currently implemented in a wide array of high level of safety-critical devices, including:

    • Those certified for Avionics DO-178B
    • Medical FDA pre-market notification (510(k)) and pre-market approval (PMA) devices
    • SIL3/SIL4 IEC for transportation and nuclear systems, 99% compliant with the Motor Industry Software Reliability Association (MISRA-C:1998) C Coding Standards


    Typical Applications:

    • Avionics - used in the Mars Curiosity Rover!
    • Medical Equipment/Devices
    • Data Communications Equipment
    • White Goods (Appliances)
    • Mobile Phones, PDAs, MIDs
    • Industrial Controls
    • Consumer Electronics
    • Automotive
    • A wide range of other safety critical embedded applications
    More Development Kits and Tools
    orangearrw.gifOperating Systems and Stacksorangearrw.gifelement14 Knode


    Key Features



    Key Features

    • Preemptive multitasking real-time kernel with optional round robin scheduling
    • Unprecedented ease-of-use combined with an extremely short learning curve enables rapid time-to-market advantage
    • Runs on the largest number of processor architectures with ports easily downloaded
    • Highly scalable (6K to 24K bytes code space, 1K+ bytes data space) I Max interrupt disable time: 200 clock cycles (typical configuration, ARM9, no wait states)
    • Sufficiently robust to meet rigorous safety-critical system requirements
    • Very Low Interrupt Disable Time
    • Delivered with complete, clean, consistent, 100% ANSI C source code with in-depth documentation.
    • Up to 254 application tasks (1 task per priority level), and unlimited number of kernel objects
    • Timeouts on ‘pend’ calls to prevent deadlocks
    • Mutual exclusion semaphores with built-in priority ceiling protocol to prevent priority inversions
    • Provides a variety of useful services: event flags; message mailboxes; message queues; fixed-sized memory partitions, task management, time management
    • Third party certifiable



    Back to top


    Technical Specifications


    General Specifications:

    • Maximum ROM Footprint (Unscaled): 24 Kbytes
    • Minimum ROM Footprint (Scaled): 6 Kbytes
    • Number of Kernel Services: 10 different using 80 API calls
    • Multitasking Model: Preemptive
    • Maximum number of Tasks: 254
    • Number of Tasks per Priotiy Level: 1
    • Code Execution Entities: Tasks, ISRs
    • Dynamic Objects: Static and Dynamic
    • Data Movement: Message Mailboxes (unlimited)and Message Queues (unlimited)
    • Semaphores - Full Counting: Yes (unlimited)
    • Mutexes - With Priority Inheritance: Yes (priority calling)
    • Event Flags: Yes (unlimited), configurable for 8, 16, or 32 bits
    • Memory Partitions - RAM Management: Yes
    • Software Timers: Yes (unlimited)



    Detailed Specifications:


    Supported processorsFPU (Floating-Point Unit) SupportYes
    MPU (Memory Protection Unit) SupportYes (μC/OS-MPU)
    MMU (Memory Management Unit) SupportYes (μC/TimeSpaceOS)
    Multicore supportAMP (Assymetrical Multi Processing)Yes
    Multitasking modelMaximum number of Tasks254 application tasks
    Clear stack at task creationYes (optional per-task)
    Run-time stack checkingYes (optional)
    Catch/delete task that returnYes
    Reentrant librariesYes (support of Thread Local Storage for compiler)
    Task registersYes (unlimited)
    Tick rateConfigurable (Typ. 1 to 100 ms)
    ISR stackUser definable hooksYes
    Task switch hookYes
    Idle task hookYes
    Statistic task hookYes
    Create task hookYes
    Delete task hookYes
    Catch task return hookYes
    Initialization hookYes
    ScalableYes (compile and run-time configurable)
    ROM (Min-Max)6K-20K (bytes)
    RAM500+ (bytes)

    ANSI-C source

    Number of source filesFewer than 25
    Argument checkingYes (optional)
    ASCII names for kernel objectsYes
    MISRA-C:2004 rulesYes (most)
    Kernel servicesTimeout on callsYes (prevents deadlocks)
    SemaphoresYes (unlimited)
    Event FlagsYes (unlimited)
    Mutual Exclusion SemaphoresYes (priority ceiling protocol)
    Message queuesYes (unlimited)
    Memory partitionsYes (prevents fragmentation)
    Software timersYes (unlimited)
    Task suspend/resumeYes
    Lock/Unlock schedulerYes
    Pend on multiple objectsYes (optional)
    Built-in performance measurementsMaximum interrupt disable timeYes
    Maximum scheduler lock timeYes
    Total CPU usage (%)Yes
    Per-Task stack usageYes
    Per-Task run counterYes
    Message pool statisticsYes
    Context switch counterYes
    Debugger Kernel Awareness SupportYes
    Third-party certificationsAvionics, DO178BYes (Level A)
    Medical, FDA 510(k)Yes
    Industrial, IEC61508Yes
    Debugger kernel awareness support IARYes


    Back to top


    Supported Devices

    Supported CPU

    μC/OS-II runs on a large number of processor architectures and ports are available (FREE download) from the knode. The vast number of ports should convince you that μC/OS-II is truly very portable and thus will most likely be ported to new processors as they become available.


    AlteraNios II
    Analog DevicesBlackfin
    Freescale68HC12, ColdFire, DSP58K, HCS12, HCS12X, M683XX, MC9S08
    Lattice SemiconductorLatticeMico32
    MicrochipPIC24, PIC32
    Renesas78K0(R), H8-300L, H8S, H8SX, M16C, M32C, R32C, RL78, RX200, RX600, SuperH 2A, V850E/2/S
    Texas InstrumentsMSP430

    Back to top




    Back to top



    Technical Documents

    Learning Center
    User ManualMicrium: μC/OS-II Configuration Manual
    Product BriefMicrium: μC/OS-II Real-Time Operating System Product Brief
    Application NoteMicrium: µC/OS-II and  Event Flags
    Application NoteMicrium: µC/OS-II and Mutual Exclusion Semaphores
    Application NoteMicrium: µC/OS-II and the ARM processor
    TutorialsMicrium: Fundamentals of Real-Time Operating Systems


    Design Element
    Application LibraryMicrium: μC/OS-II and the Microchip dsPIC33 (using C30 and the Explorer 16)
    Application LibraryMicrium: μC/OS-II and the ARM Cortex-M3 Processors
    Application LibraryMicrium: μC/OS-II and the ColdFire Architecture
    Application LibraryMicrium: μC/OS-II and the Texas Instrument MSP430F5438 (MSP430x5xx) Processor
    Application LibraryMicrium: μC/OS-II and the ST STM32 (Cortex-M3) Processorson the IAR STM32F103ZE-SK Kickstart Kit
    Application LibraryMicrium: μC/OS-II and μC/OS-View for Atmel AVR ATmega2560


    Back to top



    Ordering Information

    Licensing Options


    The user can download and evaluate Micrium μC/OS-II source code for 45 days free of charge. μC/OS-II source code may be used by accredited colleges and universities without a license, as long as the software is used only for educational purposes or peaceful research. Once the code is used to create a commercial project/product for profit, however, it is necessary to purchase a license. Micrium offers the following licensing options.


    • Single Product Licenseviewsku.bmp
      A Single Product License enables the user to embed a Micriµm software component into one end customer product. This license is perpetual for the life of the customer's product and is without limitation in production quantity. This license is specific to the processor used AND the specific name and model of the customer end product.


    • Product Line License (Product Family License)viewsku.bmp
      A Product Line License allows the user to embed a Micriµm component into any number of end products within a product family and manufacture an unlimited number of units of each of these products for the life of the end product within the product family.


    • CPU-Type License (Platform License)viewsku.bmp
      A CPU-Type License allows the user to embed a Micriµm component into any number of end products using a single and specific processor type. The license holder may manufacture an unlimited number of units of each of these products for the life of the end product.


    • Site License
      A Site License allows the user to embed a Micriµm component into any end product that uses any CPU as long as the products are designed from a single site. The user is able to manufacture an unlimited number of units from any location worldwide.


    • Dedicated Chip

            A Dedicated Chip License is exclusive to chip manufacturers. It allows you to embed Micrium software components in one type of chip, and sell that chip to an unlimited number of customers.

            It includes an instruction manual that engineers can use to get up and going in hours, with minimal risk.


    • Common to all Micrium Licenses

           All licenses are perpetual for the life of the customer’s product. All Micrium licenses are royalty free – you can build unlimited quantities of your product.

           One year maintenance is included with each new software component purchase.


    Back to top