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TP177B as Modbus Master

Created by: Navnag at: 11/29/2011 12:14 PM (8 Replies)

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11/29/2011 12:14 PM	Rate (0)
Navnag Platinum Member Joined: 11/21/2007 Last visit: 9/25/2024 Posts: 2325 Rating: (308)	Hello Wehave a requirement of connecting small HMIs on ET200S remote I/Os connected downstream of a Y-Link. We are trying to connect a TP-177B as modbus Master to ET200S - 1SI Modbus Slave at each station. The ET200S 1SI slave is working fine with Modbus Test programs ( like MODSCAN / MBPOLL ). I am able to read /. write registers in using the same. However when I connect the HMI on Modbus ( Modbus Settings are RS485, 8 Dat Bits, 1 Stop Bit, Even Parity ), I cannot establish comminication between the HMI and 1SI. In fact the HMI ( Modbus Master ) does not seem to be polling the 1SI slave as I cannot see the Rx LED blinking. What could possibly be the problem. Thanks Navnag
	There is no such thing as the last bug in a program There are no stubborn bugs, There are only stubborn Debuggers.
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11/29/2011 4:18 PM	Rate (0)
Tweety Posts: 3037 Rating: (192)	Hello, Perhaps, this FAQ can help you. What should you watch out for when connecting a SIMATIC HMI device configured with WinCC flexible ES to a SIMATIC ET 200 CPU? Tweety
Tweety Posts: 3037 Rating: (192)
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11/30/2011 4:59 AM	Rate (0)
Navnag Platinum Member Joined: 11/21/2007 Last visit: 9/25/2024 Posts: 2325 Rating: (308)	Hello Tweety Perhaps you have not understood my question. I want to connect with ET200S through Modbus RTU using 1SI Modbus slave module. Since the ET200S are connected through a Y link with S7-400H, I cannot connect the HMI directly on MPI or Profibus. Regards Navnag
	There is no such thing as the last bug in a program There are no stubborn bugs, There are only stubborn Debuggers.
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11/30/2011 4:53 PM	Rate (0)
Tweety Posts: 3037 Rating: (192)	Hello, You can see in the following manual what you can do with Modbus. See the chapter 6. SIMATIC HMI WinCC flexible 2008 Communication Part 2 Tweety
Tweety Posts: 3037 Rating: (192)
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12/1/2011 3:59 AM	Rate (0)
Navnag Platinum Member Joined: 11/21/2007 Last visit: 9/25/2024 Posts: 2325 Rating: (308)	Thanks. But I have read this, This however does not answer my basic question. Does the Modbus Driver work with RS485 / RS422 ports on the TP177B ? The WinCC Flexible allows to select the driver and RS485/RS422 port for TP177B. But it does not seem to work Regards Navnag
	There is no such thing as the last bug in a program There are no stubborn bugs, There are only stubborn Debuggers.
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12/1/2011 3:42 PM	Rate (0)
Tweety Posts: 3037 Rating: (192)	Hello, Navnag Thanks. But I have read this, This however does not answer my basic question. Does the Modbus Driver work with RS485 / RS422 ports on the TP177B ? The WinCC Flexible allows to select the driver and RS485/RS422 port for TP177B. But it does not seem to work You need for this communication on converter RS 422-RS 232. You can see this in the manual on page 29. You must attend the high-ranking numbers in the tabelle. SIMATIC HMI WinCC flexible 2008 Communication Part 2 Tweety
Tweety Posts: 3037 Rating: (192)
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12/1/2011 6:46 PM	Rate (1)
Navnag Platinum Member Joined: 11/21/2007 Last visit: 9/25/2024 Posts: 2325 Rating: (308)	Thanks Tweety. You put me on the right track. I found the problem. No, I do not need RS422 to 232C convertor ( As HMI as well as 1SI module support RS485 as well as RS422 ). instead the problem was that the Serial Port "Remote Control" was enabled in the Transfer settings. ( Also given on Page 29 ) : For a series communication in the menu "File > Transfer > Options", clear "Remote Control" from "Channel 1". Anyway, this is a good possibility of putting a HMI on S7-400H without having to use Switched Profibus through repeaters. Thanks again Navnag
	There is no such thing as the last bug in a program There are no stubborn bugs, There are only stubborn Debuggers.
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This contribution was helpful to 1 thankful Users H-H

2/8/2016 6:19 PM	Rate (0)
Bharath Sharma Experienced Member Joined: 12/7/2009 Last visit: 9/27/2024 Posts: 33 Rating: (9)	The method you found out is a theoretical solution to get a modbus RTU communication. If you try to figure out from the updated manuals, only Modbus RTU over RS232 is system tested. There is no guarantee on 485. You can actually try physically connecting a Modicon controller or some SCADA with Modbus driver & a RS485 emulator. Modicon hardware communicates well where as Simatic HMI will not. You might have done settings with Simatic hardwares & it will work since the drivers are same at both the ends. Some protocol will become true a connection will get established. To Test the same, Just take any latest HMI & just create a Modbus RTU connection. You can create some tags or leave the tag table blank. Create a field to display system time. Create a button & add StopRuntime Event to it. Download the project to HMI & check. Many a time "The time" appears not changing at all. If you stop runtime by pressing the button you created, it will reveal that the runtime has entered an endless loop. This will happen regardless of the transfer settings you do in HMI control panel. That means, only 1 Modbus query is started & it will never end. This will sometimes read or write one value to/from a partner. This may happen so since the query for profibus & modbus looks similar at lease at the start of query sometimes but finally protocol are different & there will always be an invalid or endless response from the partners. If you have found a way & are sure it works, send me your backup since many of us need more information on the same.

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4/30/2016 3:40 PM	Rate (0)
Navnag Platinum Member Joined: 11/21/2007 Last visit: 9/25/2024 Posts: 2325 Rating: (308)	No. It is not a theoretical question. We actually implemented this solution and it has been working fine for more than 6 years now.
	There is no such thing as the last bug in a program There are no stubborn bugs, There are only stubborn Debuggers.
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This contribution was helpful to 1 thankful Users H-H

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