Modicon PAC Forum
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Posted: 2022-03-15 04:52 AM
Dear All,
My customer has asked some questions related to M580 safety PLC communication blocks for which i need answers. the questions are as below,
1) What is the Maximum no. of Parallel/simultaneous TCP/IP connections that SIL CPU supports as modbus client?
2) What is the Maximum no. of Outstanding modbus requests?
3 )What is Maximum Buffer size for keeping Pending modbus requests?
I would really appreciate if someone can answer any of this
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Posted: 2022-03-16 04:02 AM
Hello,
there is no specificity with Safety - SIL Modbus communication limitations. Limitations are for Modbus TCP/IP.
You should find all the answers in the M580 Hardware Reference Manual, page 28/29
Modicon M580, Hardware Reference Manual
I hope it helps.
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Posted: 2022-03-16 04:02 AM
Hello,
there is no specificity with Safety - SIL Modbus communication limitations. Limitations are for Modbus TCP/IP.
You should find all the answers in the M580 Hardware Reference Manual, page 28/29
Modicon M580, Hardware Reference Manual
I hope it helps.
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Posted: 2022-03-16 02:42 PM
If you are talking about safe communications then you should reference the Safety Manual
https://www.se.com/au/en/download/document/QGH46982/
In this you would use
S_WR_ETH_MX / S_WR_ETH_MX2
S_RD_ETH_MX / S_RD_ETH_MX2
Which require unique ID fields for all safe communication on the network (where there could be the possibility of unintended cross-over of base communication 'channels').
This essentially means if you have 100 PLCs, each communicating to 3 PLCs, then you would have 100 x 3 x 2 (bidirectional) channels.. = 600.
The ID is an integer, so you're unlikely to run into practical limitations with this before you would start to hit network limitations.
Co-ordinating the ID fields to ensure no duplicates is generally a little trickier however. So you'd want to allow for ranges for each PLC. Perhaps allowing 10 or so 'slots', 5 in each direction. So PLC1 would get IDs 10-19, PLC2 IDs 20-29.. etc etc.
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