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TCP/IP Open modbus with 2 connections

Created by: Advantec at: 6/2/2010 1:51 PM (11 Replies)

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6/2/2010 1:51 PM	Rate (0)
Advantec Regular Member Joined: 3/3/2010 Last visit: 3/27/2024 Posts: 10 Rating: (0)	Hi, I have a 319F CPU that shall communicate with 2 identically 315F CPU's the only thing that is different is the IP adress. But when i'm testing the program against 2 modbus simulators on different PC'sthere is something that dosen't works correctly, it works some time's but not every time, Most of the time one of the connections is stopped and set to error so i have some questions: 1. can i run two connectionsat the same time? 2. I have a DB, MODBUS PARAMETER Block for each connection, is't better to have the 2 connections in the same DB

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6/2/2010 2:35 PM	Rate (2)
smiffy Platinum Member Joined: 1/17/2007 Last visit: 10/21/2024 Posts: 1547 Rating: (537)	Advantec 1. can i run two connectionsat the same time? Yes you can provided that they are on different source (local) ports. Obviously, they would have different ID in NetPro. You would require 2 modbus blocks and the modbus blocks would have to be setup accordingly. Advantec 2. I have a DB, MODBUS PARAMETER Block for each connection, is't better to have the 2 connections in the same DB That would be a better idea. There is no technical reason why this should not work (I have done it with my own modbus driver block that I developed). However, I am not sure how the Siemens block would handle it. You would have to ask someone from IT4Industry as they developed the modbus block. You could post the question on the TCP modbus forum in the IT4Industry section and see what they say. Or you could just try it and see what happens. It has 2 chances!
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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6/2/2010 7:17 PM	Rate (0)
Tomcat Posts: 433 Rating: (48)	Hi, you can use 1 modbus parameter data block with 2 connections and you can use 2 modbus parameter blocks with 1 connection per data block. It's no difference in the modbus block. Which errorcode occurs? I often use multiple connections and it works perfectly. Can you attach your project here? Tomcat
Tomcat Posts: 433 Rating: (48)
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6/3/2010 8:45 AM	Rate (0)
Advantec Regular Member Joined: 3/3/2010 Last visit: 3/27/2024 Posts: 10 Rating: (0)	Hi again, The error code A080 without i have change any thing in the DB_PARAM I have attached the project or only thepart that i use with the modbus connections. This is the first time for me working with this TCP/IP open modbus. When i hade program the first connection (called PLC A) in project it works perfecly then i copied this logic for the (PLC B) and modified it for the PLC B connection and when i started testing it connection with PLC A works perfectly but connection with PLC B i have manage to work a few times but at the most time it comes in to error. Regards Advantec Attachment Modbus.zip (772 Downloads)

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6/3/2010 11:54 AM	Rate (0)
smiffy Platinum Member Joined: 1/17/2007 Last visit: 10/21/2024 Posts: 1547 Rating: (537)	The error code A080 is given as: The connection 0A is not initialized. This would suggest that there is a problem with the connection. Have you parameterised the ID_0_A and LADDR_0 inputs correctly? Have you checked that on-line status of both connections is shown as "established" in NetPro? I cannot open your project, as my PCS7 install at work is an eralier version. I will look at it tonight when I get home.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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6/3/2010 1:23 PM	Rate (0)
Advantec Regular Member Joined: 3/3/2010 Last visit: 3/27/2024 Posts: 10 Rating: (0)	Hi, Iwant to communicate via the integrated PN interface of the PLC and thata configuration in NetPro was not necessary?? That is what the manual for S7-Open Modbus /TCP Communication via the integrated PN interface of the PLC says... Regards Advantec

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6/3/2010 2:58 PM	Rate (0)
smiffy Platinum Member Joined: 1/17/2007 Last visit: 10/21/2024 Posts: 1547 Rating: (537)	Ah you are using the PN CPU. I didn't noticed that. That changes things a bit. Error code A080 is given as "The parameter DB_PARAM was changed without a restart of the CPU." Which sounds like you have changed the DB_PARAM number or the contents of the DB_PARAM DB during runtime. Here is the relevant section out of the manual:- The parameter of data block MODBUS_PARAM must not be changed during runtime. It is necessary to restart the PLC after the modification of MODBUS_PARAM. For each logical connection one structure is required. Reading the manual, the way I understand it is that you would have to add a new structure to the DB for each logical connection. I cannot say for certain as I have never used this block. I suspect that you only have one structure in the DB and are attempting to modify it's contents during runtime to use another connection. Is that the issue? @Moderators: This thread might best being moved to the IT4Industry->Open Modbus TCP forum, where it will be seen by the Open Modbus TCP experts.
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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6/3/2010 3:30 PM	Rate (0)
Advantec Regular Member Joined: 3/3/2010 Last visit: 3/27/2024 Posts: 10 Rating: (0)	Yes buti have restarted the PLC after everymodification but the same error code isgenerated. I will try to put both connections in one MODBUS_PARAM but it also says in the manual: "The parameter data block can contain parameter information of all defined connections. It is also possible to use a separate parameter data block for each connection" I have a separate parameter data block for each connection. Today i don't have the 2 PLC's that i shall connect to so i simulate the connections with 2 PC's with a modbussimulator oneach. The connection to the first modbus simulator works perfectly but the connection to the second modbus simulator dosen't work! the errorand error code is generateddirect after a restart of PLC?? Advantec

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6/3/2010 9:58 PM	Rate (0)
Tomcat Posts: 433 Rating: (48)	Hi, I found the reason for your problem. Open the OB100 and delete the BEB in the first network. Because of this BEB the second connection is not initialized. Tomcat
Tomcat Posts: 433 Rating: (48)
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6/5/2010 10:54 AM	Rate (0)
Advantec Regular Member Joined: 3/3/2010 Last visit: 3/27/2024 Posts: 10 Rating: (0)	Hi again, Yes i also find the problem in OB100 Thanks now it works perfectly!! Best Regards Advantec

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