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best mode of communication between S7 400 plc and 4 panels, Modbus TCP or Modbus RTU)?

2/9/2014 8:53 AM	Rate (0)
S7 AUTOMAN Posts: 515 Rating: (56)	hi all, what is the best mode of communication between an S7 400 plc and 4 other third party addressable panels? The distance between all these panels will be not more than 200 meters and the communication link will be partly immersed in salt(sea) water as well. which mode of communication should i opt(Modbus TCP or Modbus RTU)? Also the main controller (S7 400 PLC) should have a redundant Modbus RTU communication with the DCS(Master) apart from this. So in the first case S7 400 acts as the master(if we opted Modbus RTU) wheras in the second case it acts as a slave. So what all components and softwares should i consider to achieve this(in case Modbus RTU selected)? Kindly help me out at the earliest please
S7 AUTOMAN Posts: 515 Rating: (56)	Last edited by: S7 AUTOMAN at: 2/10/2014 8:45 AM Last edited by: GrasserF at: 2/10/2014 7:13 AM new subject after splitting from /tf/WW/en/Posts/102524 Last edited by: S7 AUTOMAN at: 2/9/2014 8:55 AM
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2/10/2014 8:42 AM	Rate (0)
S7 AUTOMAN Posts: 515 Rating: (56)	hi, Anyone could please help me out with this at the earliest
S7 AUTOMAN Posts: 515 Rating: (56)
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2/10/2014 9:36 AM	Rate (0)
Sakura Silver Member Joined: 9/22/2010 Last visit: 2/10/2025 Posts: 225 Rating: (28)	Hello S7 Automan, if you decide to use Modbus TCP, you either need a PLC with an integrated PN interface or an additional CP 443-1 and license for a Modbus TCP library. When using a PN PLC you need the license 2XV9450-1MB02. When using a PLC and a CP 443-1 you need the license 2XV9450-1MB00. You can find further information about these Modbus TCP libraries here: http://www.siemens.de/s7modbus I'm afraid I don't know if Modbus RTU or Modbus TCP is better in your setup. Regards Sakura

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This contribution was helpful to 1 thankful Users S7 AUTOMAN

2/10/2014 9:41 AM	Rate (0)
S7 AUTOMAN Posts: 515 Rating: (56)	hello sakura, Thank you for your suggestion. But can Modbus TCP cover a distance of upto 200m without switches/repeaters? Also note that since the medium is salt water, use of repeaters/switches is practically impossible.And also the communication link should withstand the corrossive environment. And also i actually needed the components for Modbus RTU communication as both master and slave if it is apt.
S7 AUTOMAN Posts: 515 Rating: (56)	Last edited by: S7 AUTOMAN at: 2/10/2014 9:49 AM
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2/10/2014 10:36 AM	Rate (0)
Sakura Silver Member Joined: 9/22/2010 Last visit: 2/10/2025 Posts: 225 Rating: (28)	I'm afraid I neither have a deep knowledge about the different kind of cables nor about Modbus RTU :( I guess for Modbus TCP for covering 200m without a switch/repeater a fiber optic cable is needed. So I assume Modbus RTU would be the right choice in this case. But I can't do more then guessing here...

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This contribution was helpful to 1 thankful Users S7 AUTOMAN

2/10/2014 11:09 AM	Rate (0)
S7 AUTOMAN Posts: 515 Rating: (56)	Thank you. Anybodyelse could please give me some valuable suggestions regarding this
S7 AUTOMAN Posts: 515 Rating: (56)
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