1.3.10. Hardware and Operating System Abstraction Layer (Sys-Components)

The hardware and operating system abstraction layer is covered by the so called system interface components. Each system component is designed for a special assignment and a logical operation system object.

The description of all available system interfaces declared in detail in the system reference guide of the runtime system (“Reference” in runtime help).

1.3.10.1. Time access (SysTime)

In this component, you can have access to ticks with different resolutions (millisecond, microsecond and nanosecond) for e.g. time measurements and access to some functions of the real time clock (RTC).

1.3.10.2. Serial interface (SysCom)

This component provides access to a serial device (RS232). You can open and close a device, specify settings to the device and read and write data to this device.

1.3.10.3. Exception handling (SysExcept)

The first level exception handling is done in this component. This component realizes on different platforms and operating system a defined exception handling.

If the exception is caught, the register set of the processor will be investigated (and the task, if available) and will be forwarded to the task or timer component to investigate the source component of the exception.

With the processor context a call-stack can be investigated by higher level exception handling components.

1.3.10.4. File access (SysFile)

This component provides routines for file access. You can open or close a file, read from or write into a file, delete or rename a file, set and get the actual file pointer in a file and so on.

One thing is quite important:

At the routines where a file name is specified as a parameter, there are two different implementations. E.g. to open a file can be done in with two different interface functions:

SysFileOpen(char *pszFile, ACCESS_MODE am, RTS_RESULT *pResult)
SysFileOpen **_** (char *pszFile, ACCESS_MODE am, RTS_RESULT
*pResult)

The only difference between the SysFileOpen and the SysFileOpen_ is the handling of the file names. If a path (absolute or relative) is specified in the file name, the path is used unchanged.

If no path is specified in the file name, the two functions work different:

In SysFileOpen, a default path is added to the file name by the runtime system. For the SysFile component, paths can be specified for each ending of the file name.

In SysFileOpen_, no default path is added and the actual working directory is used.

This difference in path handling is identical for all SysFileX and SysFileX_ routines.

1.3.10.5. File access using flash (SysFileFlash)

As an alternative to SysFile (see File access (SysFile)), this component provides routines for file access. You can open or close a file, read from or write into a file, delete or rename a file, set and get the actual file pointer in a file and so on.

As a difference, this component does not use the file system of an operating system, but uses the SysFlash component.

A basic file system is implemented. It is based on a static table of files, with fixed file names and maximum file sizes.

The file table has to be defined in sysdefines.h in variable FILE_MAP. An example is provided in the header file of the component.

1.3.10.6. Flash access (SysFlash)

This component provides routines for flash access. The usage of this component is optional. It provides functions to write a data buffer to flash, read from flash, and get the address and size of the flash. It contains also a function that is called when a flash based file is closed.

The flash can be used as

• a basis for the SysFileFlash component, and

• for optional execution of the user code in flash. This can be used to

  reduce the RAM memory requirements.

  1. Directory handling (SysDir)

The directory component provides access to a file system. Directories can be scanned, created, deleted or renamed.

1.3.10.7. Memory access

The handling of memory is provided by the SysMem component.

Heap and static memory (SysMem)

To access the heap memory (dynamic memory allocation), there are different routines to allocate and free code and data memory. Code memory can be used to execute code in this memory.

To access static memory for the PLC application, there is a function called SysMemAllocArea(). Here a static memory for the code and data area for the PLC application can be specified.

Physical memory access and shared memories (SysShm)

To get access to physical memory (e.g. dual port RAM of a card), the SysShm provides routines to map the physical memory into the memory of the runtime system.

1.3.10.8. Dynamic loading module (SysModule)

The dynamical load of components can be used on targets with an operating system. This functionality is provided by the operating system and can be used via the SysModule component.

The components must be available in a dynamical loadable format (e.g. under Windows a Dll, under VxWorks an o-file).

1.3.10.9. Ethernet sockets (SysSocket)

The access to the TCP-stack, the SysSocket can be used. The socket interface provides TCP, UDP and RAW sockets.

The SysSocket component provides additionally more higher level interfaces, to set up a TCP or UDP client and server.

1.3.10.10. Debug console outputs (SysOut)

To print messages at the console (if available), you can use the SysOut component. This component is used for example by the logger, to print all log entries at the standard console output.

1.3.10.11. Message queues (SysMsgQ)

MessageQueues are a special higher level object to use for inter thread and task communication. The message queues are thread-safe and are used in the runtime system for example for the time slicing implementation of the Scheduler.

1.3.10.12. Interrupt handling

Interrupt handling is a very low level and platform dependent component. This component provides routines to open an interrupt and to register an interrupt handler to this interrupt. All interrupt can be enabled or disabled with this component too.

1.3.10.13. PCI bus access (SysPCI)

This component provides access to the PCI bus. The PCI configuration can be read and written for example to auto detect cards that are plugged in the PCI bus.

1.3.10.14. Device port access (SysPort)

Accessing devices is typically done via so called ports. The SysPort component provides access to devices via these ports. Port values can be read and written.

1.3.10.15. Timer handling (SysTimer)

Timer devices can be used for processes with a strong time constraint. The SysTimer component provides access to timer devices on the target. Timers are typically used in the runtime system for the cyclic call of the runtime scheduler or to execute IEC tasks with the specified cycle times.

1.3.10.16. Target information (SysTarget)

The SysTarget component provides access to the target information like vendor and device name, target Id and version or the node name for the communication. The node name is detected in some implementations from the node name of the operating system that was assigned to the target. There are two possibilities to overload the target information:

• Compatible way: overloading the SysTarget component (e.g. by SysTargetOEM). The whole SysTarget interface has to be implemented in this case and the new component replaces the existing SysTarget implementation in the runtime.

• Preferred way: overloading by event. Selected target characteristics can be overloaded in an event callback at startup of the runtime.

1.3.10.17. Task handling

These components are only available on operating systems with tasks or threads

Synchronization and semaphores (SysSem)

To synchronize access to common data between several tasks or threads, the SysSem component can be used to handle synchronization objects, called semaphores.

Operating system events (SysEvent)

To activate tasks or threads, the operating systems provides events to activate a task from another task.

Task handling (SysTask)

The SysTask component provides routines to create and delete tasks, to suspend (set into sleep) and resume (wake up) tasks and so on.

1.3.10.18. Optional system components for target visualization

There are optional system components that are needed by the CODESYS target visualization. These components can be added to the runtime system, if a graphical interface on the target is available.

Window handling (SysWindow)

The SysWindow component provides access to the window handling of the graphical environment. The target visualization typically runs in a window.

Basic graphic routines (SysGraphic)

The target visualization uses some basic graphic operations to display all visualization objects. These basic operations are provided by the SysGraphic component.

With earlier versions, the size of JPEG images in the Windows and Windows CE target visualization was limited to 1024*768*3 bytes (approx. 2.3 MB). As from V3.5.1.0 the limit can be configured by an entry in the PLC configuration file CODESYScontrol.cfg:

[SysGraphic]
Win32.MaxJpegByteArraySize=5000000

Note however: The limit should not be chosen too big in order not to waste memory and because the CE CreateDIBSection function may fail with 10 MB pictures.

1.3.10.19. Process handling

On operating systems with the possibility to use processes, there are some components to use these processes. This components are typically used in the runtime system to spawn an own process of the target visualization to separate the runtime system from the part that displays the graphic information of the target visualization.

Processes (SysProcess)

The SysProcess component provides access to create and delete processes.

Process synchronization (SysSemProcess)

To synchronize access to common data objects from several processes, the SysSemProcess component provides access to process semaphores.

1.3.10.20. Direct Ethernet controller access (SysEthernet)

This component provides direct access to an Ethernet controller. This is typically used by the EtherCAT drivers to get direct access to an Ethernet controller.