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IEC 61131-3 Function Blocks support remote application programming via modemRalf Wohlschläger, EURO-Matsushita Electric Works AG
Remote control applications are relatively new and the number of applications has rapidly increased since 1992 when Matsushita entered this market and began to develop expertise with this type of product.
Remote control and monitoring of programmable controllers can be achieved via different telephone network technologies and since typical PLC programmers are not experts in telecommunications, the automation systems suppliers have to offer ready-made solutions for both hardware and software communication components. The Function Block (FB) concept is typical of the type of solution offered by automation systems companies. The IEC 61131-3 supported Function Blocks allows all the special telecommunications know-how to be incorporated in to Function Blocks so that the end-user can integrate the ready made software block without any telecommunication knowledge.
Depending on the application and the environment, several communication methods based on the following connection options can be offered :
All of these technologies require ready made function blocks that cover device initialisation, dial-up and disconnection, communication and handshaking, password protection to avoid unauthorised users and the management of the priority / Master-Slave hierarchy.
To cover the different hardware architectures and software options for each concept, Matsushita offers an extensive software library with many IEC 61131-3 Function Blocks for easy integration into user programs - the largest FB in the Matsushita library has 1,200 program steps. The FB MODEM shown below is an example from the Matsushita Library.
(Screen dump of Function Block not drawn here)
Remote control applications are the best example of the advantages of the IEC 61131-3 and the easy reusability of available software. It would be almost impossible for the traditional PLC programmer to collect all the knowledge and detail about telecommunications and then use it in an efficient way. However, with the IEC 61131-3 Function Block concept, this has been achieved since telecoms experts have investigated and programmed the required tasks in to ready made blocks which can be reused without knowledge of the complex contents.
The use of remote control is increasing and there are many applications examples:
The advantages of modem remote control for the industry are significant: