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Michael Griffin wrote:>
> Something which really hasn't been mentioned too much is that
>if a variety of different hardware ran the same "soft logic" system the end
>customer would be able to separate the issue of what hardware to use from
>what software to use.
At the Instruction List level, most of the major PLC's appear to offer much the same capabilities, even though their architectures differ (S7 is based on a 2-register model, etc). There appears to have been no effort to define a standard for PLC's at this level (similar to JAVA bytecodes or Microsoft's Common Language Infrastructure, but doing so could provide a common target language for all configuration tools, Ladder, FB, SFC's, etc. The extra step of translating this common instruction set into each manufacturers own code
should be fast and easy to optimise for each hardware platform, though the ideal would be for different firmware which would interpret the standard language directly.
Both IEC61131 and IEC61499 do not define any standard target platform, and so instead of being able to use any configuration package of choice, we now have a proliferation of 'IEC-61131 compatible' programming tools, each usable only with one hardware platform, and each with its own version of Ladder, etc.
At the PC level, MS CLI is generating a lot of interest, with the MONO project aiming to host this on a Linux platform. A parallel effort for PLC's would appear to be very worthwhile. What are the technical difficulties? What machine instructions do current PLC's work with? At what level are the individual programming languages such as STL translated or interpreted?
What debugging/monitoring API's are used? Is any of this made available?
I am aware of the LinuxPLC project, but unless some common approach is taken, it would seem to offer Yet Another Learning Curve even if it is totally successful.
Hywel Thomas
CONTROL SPECIALISTS LTD, UK
> Something which really hasn't been mentioned too much is that
>if a variety of different hardware ran the same "soft logic" system the end
>customer would be able to separate the issue of what hardware to use from
>what software to use.
At the Instruction List level, most of the major PLC's appear to offer much the same capabilities, even though their architectures differ (S7 is based on a 2-register model, etc). There appears to have been no effort to define a standard for PLC's at this level (similar to JAVA bytecodes or Microsoft's Common Language Infrastructure, but doing so could provide a common target language for all configuration tools, Ladder, FB, SFC's, etc. The extra step of translating this common instruction set into each manufacturers own code
should be fast and easy to optimise for each hardware platform, though the ideal would be for different firmware which would interpret the standard language directly.
Both IEC61131 and IEC61499 do not define any standard target platform, and so instead of being able to use any configuration package of choice, we now have a proliferation of 'IEC-61131 compatible' programming tools, each usable only with one hardware platform, and each with its own version of Ladder, etc.
At the PC level, MS CLI is generating a lot of interest, with the MONO project aiming to host this on a Linux platform. A parallel effort for PLC's would appear to be very worthwhile. What are the technical difficulties? What machine instructions do current PLC's work with? At what level are the individual programming languages such as STL translated or interpreted?
What debugging/monitoring API's are used? Is any of this made available?
I am aware of the LinuxPLC project, but unless some common approach is taken, it would seem to offer Yet Another Learning Curve even if it is totally successful.
Hywel Thomas
CONTROL SPECIALISTS LTD, UK