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Modbus communication with Simatic S5 CP521
May 6, 2008 6:16 pm, by Nishad
Subject : Communications
 from the control system dept.
Text :
Hello,
We are facing a problem in the communication of Simatic S5 100U CPU-103: 6ES5 103-8MA03 (CP521 Printer interface card: 6ES5 521-8MA11) with ABB 800xA system (CI853-Serial communication card).
Simatic S5 system is presently communicating with Yokogawa Microexcel's DCS RS2 (Suffix C) card. We don't know exactly about the communication protocol used with Yokogawa Microexcel system. Our requirement is to establish communication of Simatic system with ABB 800xA system via Modbus.
Does CP521 card support Modbus communication?
If not, is there any mode of communication available?
We need help from your side for this issue.
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Re: Modbus communication with Simatic S5 CP521
May 8, 2008 1:07 am, by Patrik
Hi there,
One way of solving the problem could be to use a gateway. I assume that your Simatic S5 acts as Profibus master and that the ABB 800xA acts as Modbus master. In such a case, a gateway that is a Profibus slave and Modbus slave would be work.
For more info of the gateway, go to:
http://www.anybus.com/support/support.asp?PID=185&ProdType=Anybus%20X-gateway
or email me at: support@hms.se
/Pat
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Re: Modbus communication with Simatic S5 CP521
May 8, 2008 12:32 am, by Michael Griffin
There is a special memory module that you can get to plug into most models of CP521. This memory module has firmware with the Modbus RTU protocol programmed into it. I think you also need some special function blocks in the PLC CPU so the CPU will talk to the CP521 (I think these come on a disk). However, there are several different models and versions of CP521. I don't know if this works with the one you have. You'll have to look that up for yourself on the Siemens web site.
If your CP521 has a memory module plugged into it, it may have Modbus RTU already. You would need to read the part number off the memory module and look it up on the Siemens web site. A memory module (if present) is an optional part, so it has a separate part number from the CP521 itself.
If you already have Modbus, then you need to make sure things like baud rate, parity, etc. are all set correctly. I would suggest looking up more information on the Yokogawa system so you can find out what it is already doing.
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