R8C Family General RTOS Concepts
The concept is orthogonal to that of micro- vs. monolithic kernels by giving an application efficient control over hardware. It runs only services protecting the resources (i.e. tracking the ownership, guarding the usage, revoking access to resources, etc) by providing low-level interface for library operating systems (libOSes) and leaving the management to the application.
Figure 6 Exokernel Based Operating System
An RTOS generally avoids implementing the kernel as a large monolithic program. The kernel is developed instead as a micro-kernel with added configurable functionalities. This implementation gives resulting benefit in increase system configurability, as each embedded application requires a specific set of system services with respect to its characteristics.
The kernel of an RTOS provides an abstraction layer between the application software and hardware. This abstraction layer comprises of six main types of common services provided by the kernel to the application software. Figure 7 shows the six common services of an RTOS kernel.
Figure 7 RTOS Kernel Services
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