1.2.1. OverviewΒΆ
In the following figure you can see an overview of the architecture of the runtime system.
The base component is the component manager. This is the central component that must exist in every runtime system. The component manager loads and initializes all components and enables the connections between the components.
The second important part consists of the so called system components. These components represent the hardware and operating system abstraction layer and hide processor and operating system specific stuff from all other components. Via this system interface, all other components can be written absolutely portable and independent of processor and operating system internals. Every system component has its specific functions, e.g. file access, access to heap memory, access to a serial RS232 interface, operating system tasks, etc. All system components are described in Overview of the Kernel Components and Main Functions.
The third part is the communication stack. It consists of several components to enable the communication to clients (CODESYS, HMI, etc.) or to other runtime systems. For the last issue, a routing mechanism is additionally provided by the communication stack.
At the bottom of the stack there are the so called block drivers. Each of them provides one single communication medium (e.g. UDP, a TCP/IP protocol via Ethernet). The block drivers use the system components to get a neutral access to the physical layer.
The next layer in the communication stack is the router. It provides routing to each runtime system in a hierarchical network that consists of CODESYS Control V3 runtime systems.
Above the router, there are special service components e.g. for address assignment in the network, identification of a runtime system or the level 4 server for the block communication.
Each service request from a client first is received by the level 7 server. Each service is assigned to a specific group of services and then is forwarded to the special server, that was registered to the special service group.
In the architecture overview figure shown above you can see, that the communication stack is an integrated part of the runtime system. The gateway from version 2.x of CODESYS on version V3 is a special derivate of the runtime system that consists only of the component-manager, some system components and the communication stack for detailed information)!
The fourth part consists of the application management components. Here the execution, debugging and monitoring of the IEC application(s) is done. A completely new feature in CODESYS Control V3 is the management of several applications on ONE runtime system! This offers a lot of new application possibilities. The PLC task handling is separated up in two components: the IEC task manager and the scheduler. So a new scheduler algorithm can be provided only by replacing the scheduler component.
The last but not least part consists of the core components. These components provide the remaining functionality of a runtime system. The configuration of the runtime system, the logger to log all states and the device component for authentication reside here. The memory management and the event handling (for runtime events) are two additional components of the core.
For OEM customers there are several ways to extend the runtime system.
You can:
Replace existing components
Write own plugins (block drivers, IO-driver)
Write OEM components with external libraries, own service handling, etc.