Hard Real-Time with Windows XP
Modular System
For AUTOMATIONWORX, Phoenix Contact uses modular firmware, in which certain functions are realized using dedicated modules. This modular firmware is designed in such a way that it is initially independent of the operating system, but it still must be adapted to each new system, with certain costs attached. Phoenix Contact did not need to meet these costs when adapting the firmware to CeWin, as it was easy to implement. Smaller tasks arose only when integrating the network, so that it would already be available when the firmware was started.
The firmware is structured in such a way that when operating on a real-time system, the files are accessed simultaneously: the computer accesses them, and can either read them, or receive a read error in response. As a result, these calls are no longer deterministic when they have been conducted via the network drive. It could therefore take an indeterminate amount of time, in theory, before the function call returns. In this case, the firmware would simply block, and therefore the real-time behavior would be partially lost. Here, Phoenix Contact had to insert an interim layer, as it is, in order to make each of these calls asynchronous. An "asynchronous mechanism" is created for the access to the network drive: if the calls have not been completed within a specified time period, the call always returns to the firmware. It was necessary for Phoenix Contact to develop this interim layer.
CeWin: software with a past and a future
The real-time implementation of CeWin is derived from KUKA Controls' VxWin® product, which has been in use for ten years. KUKA is one of the world's leading suppliers of industrial robots, including control systems and software. VxWin was developed by KUKA Controls, a subsidiary of KUKA Roboter GmbH. On the real-time side, it uses VxWorks® (instead of Windows CE with CeWin), with Windows XP on the user interface.
Since Version 4.2, Windows CE has been excellently suited to real-time tasks, and Version 5.0 has meanwhile become available as a genuinely hard real-time operating system. CeWin incorporates the same basic principle and uses the same technology and the same drivers as VxWin.
The KUKA Controls products therefore act as bridges between VxWorks and Windows XP (VxWin), as well as between Windows CE and Windows XP (CeWin). VxWorks may now have a real rival in the form of Windows CE, but KUKA Controls is giving both real-time operating systems the same long-term support, in order to cover a broad market with several different options.
With VxWin, developers work with Windows XP and the Win32 for user interface and connectivity development, while on the real-time VxWorks side they use a POSIX environment which is closer to the UNIX environment in terms of the type of programming involved. However, with CeWin, developers work with a Win32 API on both sides, thus using a highly homogeneous solution. When two Windows computers are operated on a single network, the hard drives can be connected with each other via the Map network drive function. This means that CeWin can use the Windows XP hard disk via the shared memory network in the same way as a local drive. With VxWin, extended measures are required for this purpose, since here, the drive managed by Windows XP must be accessed via FTP (File Transfer Protocol).
Other companies in the IWKA Group, as well as many suppliers of automated solutions, are using VxWin and CeWin. Since this software fulfils a strategic goal within IWKA, VxWin and CeWin customers can rest assured that optimum support will be provided for the product now and in the future. KUKA Controls is already extensively involved in designing new versions for the follow-up to Windows XP, Vista (formerly known as Longhorn).
KUKA Controls is also developing a module, which will enable the precise synchronization of several machines down to the microsecond level via a standard Ethernet, in accordance with IEEE 1588. Additional packages supporting real-time Ethernet standards like PROFINET or EtherCAT can also be provided.
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