Micriµm: µC/OS-III Real-Time Operating System Kernel Overview

Overview

µC/OS-III is a highly portable, ROMable, scalable, preemptive, real-time, deterministic, multitasking kernel for microprocessors, microcontrollers and DSPs. μC/OS-III is Micrium’s newest RTOS, designed for developers who need to save time on their current and next embedded sytem projects. Using a commercial real-time kernel such as μC/OS-III provides a solid foundation and framework to the design engineer dealing with the growing complexity of embedded designs. μC/OS-III is a complete new real-time kernel with roots in μC/OS-II.

In addition to the features inherent in μC/OS-II, μC/OS-III also manages an unlimited number of application tasks, and features an interrupt disable time of near zero. μC/OS-III manages unlimited application tasks, constrained only by a processor’s access to memory. μC/OS-III supports an unlimited number of priority levels. Typically, configuring μC/OS-III for between 8 and 256 different priority levels is adequate for most embedded applications. µC/OS-III allows multiple tasks to run at the same priority level. When equal priority tasks are ready-to-run, µC/OS-III runs each for a user-specified amount of time. Each task can define its own time quanta and give up its time slice if it does not require the full time quanta.

Besides unlimited  taks management, other services μC/OS-III provides include unlimited tasks, semaphores, mutexes, event flags, message queues, timers, memory partitions, and more. The user allocates all kernel objects at run time. μC/OS-III provides features to allow stack growth of tasks to be monitored. While task size is not limited, they need to have a minimum size based on the CPU used.

μC/OS-III has a number of internal data structures and variables that it needs to access atomically. It protects these critical regions by disabling interrupts for almost zero clock cycles, ensuring that it is able to respond to some of the fastest interrupt sources. Interrupt response with μC/OS-III is deterministic.

µC/OS-III provides extensive range checking which can be disabled at compile time.  µC/OS-III thus checks for NULL pointers passed in API calls, task level services from ISRs aren’t called, arguments are within allowable range, and specified options are valid. Each API function provides an error code regarding the outcome of the function call.

μC/OS-III’s footprint can be scaled to only contain the features required for a specific application. The execution time for most services provided by μC/OS-III is both constant and deterministic; execution times do not depend on the number of tasks running in the application

Typical Applications:

• Data Communications Equipment
• White Goods (Appliances)
• Mobile Phones, PDAs, MIDs
• Industrial Controls
• Consumer Electronics
• Automotive
• A wide range of embedded applications

• Preemptive multitasking real-time kernel with optional round robin scheduling
• Delivered with complete, clean, consistent, 100% ANSI C source code with in-depth documentation.
• Highly configurable
• Intuitive Application Programming Interface (API)
• Preemptive Multitasking: Runs the most important task that is ready
• Nested task suspension
• Very Low Interrupt Disable Time
• Scalable to contain only required features
• Highly scalable (6K to 24K bytes code space, 1K+ bytes data space)
• Mutual exclusion semaphores with built-in priority inheritance protocol to prevent priority inversions( Mutexes)
• Built-in performance measurements for execution time of each task, stack usage of each task, number of times a task executes, CPU usage, ISR-to-task and task-to-task response time, interrupt disable time, and more
• Timeouts on ‘pend’ calls to prevent deadlocks
• Third party certifiable