The Hardware Memory Protection Units
Our Space Protection Extension complements the real-time kernel µC/OS-II from Micrium to the possibility of comfortable use of memory protection units of modern microcontrollers. Requirement is one of the widely available memory protection units:
- Memory Management Unit (MMU) or
- Memory Protection Unit (MPU)
The Memory Management Unit (MMU) and the Memory Protection Unit (MPU) are memory protection units and are designedto control access to memory. The memory management unit additionally has the option to perform an address transformation, that is real memory addresses (so-called "physical addresses") are translated to desired addresses (so-called "virtual addresses").
Functions of real-time kernel µC/OS-II
All service functions of the proven real-time kernel µC/OS-II remain unchanged. Thus a switch of a system is possible. The possibilities of the real-time system with memory protection are composed of the RTOS services and the functions for Space Protection:
- Preemptive Multi-Tasking
- Software Timer
- Process Memory Protection
- Memory Management
- Shared Memory
The management of the write access to memory areas is set up using service function calls. Such a managed storage area is called process. Following one or more tasks can be assigned to the process.
All services of µC/OS-II are unchanged and can be used as usual. For all services of Micrium's µC/OS-II, which are used for synchronization and communication, we have used a zero-copy technology.
In addition to the proven services of µC/OS-II we add a shared memory service within the extension. This service allows sharing of storage areas with write access for tasks from different processes.
The real-time kernel undergoes regular improvements and additions from our safety-critical projects. We always pay attention to the goal of a real-time kernel: Best performance and maximum safety.
Growing Number of Supported Micro Controller
Available RTOS Systems with Space Protection
See below an extract of existing RTOS Systems with Space Protection. We have designed the Space Protection Extension to add new microcontroller for any RTOS very fast and with low effort.
|Cortex A9||Altera SoC||ARM|
Code Composer Studio
Code Composer Studio
If your microcontroller is not listed, just ask us. We are working continuously on new systems.
We compiled some information about the memory protection units within different cores for you.
The ARM9 core includes a MMU unit. The MMU is organized with tables of two levels, stored in RAM. The evaluation of the tables (the so-called "Table-Walk") is completely performed in hardware.
The Cortex-A family includes a MMU. This MMU is a evolution of the ARM9 family MMU. This MMU supports better control of Caches and optionaly supports Multi-Core features.
The Cortex-M3 includes a MPU. The MPU units are optional and can be activated by the chip vendors. Since the Cortex-M3 microcontrollers are often designed for small, low-cost applications, the MPU is often disabled. Therefore check the datasheet of the chip manufacturer, if you want to take advantage of memory protection.
The Cortex- M4 core includes an MPU. In this core family the chip manufacturer must enable the MPU. The performance of the Cortex-M4f is in a regionwhere the MPU is usually enabled. For safety, we recommend: please check the datasheet of the chip manufacturer, if you want to take advantage of memory protection.
Note: A special feature is in the Kinetis microcontroller family (NXP, former Freescale). In these microcontrollers the MPU from ARM is disabled, and in some devices a different implementation by Freescale is integrated.
The Cortex-R family includes a MPU. This MPU has been activated in all microcontrollers from all chip vendors we have seen. Well, this makes sense, as these chips are intended mostly as "Safety Chip", and therefore the memory protection is most beneficial.
The TriCore includes a MPU. The Aurix is a Multi-Core microcontroller with multiple TriCores for safety-critical applications. This chip includes multiple MPUs separately for bus system, peripherals and memory.
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Related products and services
The so-called "Cert Kit" is the real-time kernel with memory protection - completely approved for applications with Functional Safety. For more details, read: Pre-Certified Real Time Kernel
Our experience is available within your project, too. With adjustments and optimizations of existing real-time kernels to specific requirements in your project, we can realize your ideas. For more details, read: Service: Functional Safety