1. Modbus Tcp Library

My Problem is that after sending the write request I want to close the port again. But the program throws me because the Serialport is busy. I thought the best would be to read the responding message and then close the port. But it would be possible just to wait some time till it is not busy anymore and then close it. (Maybe with a timer) What is the best way to deal with this problem? I think everybody who works with Modbus has to solve this So there should be a common way to do it.

Thanks for the Support here. Thank you Mesta, I know that the normal Response is the same query that the master wrote. But if the writing fails it responds with another message. So it would be nice to read the message. But I if it is not usual to read the Response I don´t need to read it.

Are you sure the S7-200 uses Modbus? You can download working VB Modbus project from www.modbus.pl. Modbus/USS library for Microwin. Jul 24, 2009  Dears, I´m need of a example of S7-200 in Modbus Slave using the freeport. If anybody have a application running without the library. Using the Modbus Master Protocol Library. Libraries makes commun icating to Modbus slave devices easier. The S7-200 to act as a Modbus RTU. Free font with swash tail.

Not the general simple solution I was looking for so I think if I want an event driven communication it’s better to go with some OPC-solution which has already solved what I’m looking for. Do you know how this is solved under the hood of the OPC-server? Is the OPC server polling the device? Hi Eric, probably you are confusing the two libraries, but S7.Net use S7 protocol, nModbus use Modbus protocol (that depending on the physical cable can be Modbus TCP (ethernet) or Modbus RTU (RS 422 – RS 485). S7.Net use Profinet (or Industrial Ethernet, don’t remember that good) and it’s derived from LibNoDave that can communicate both with Profinet and MPI. To use nModbus you need to add the Modbus libraries to the plc program. About Master and Slave, think like internet: a website is the Master and your pc that browse the site is the Slave.

(sorry for my bad english 🙂 ) Best regards. Hi, Thanks for your answer. I Read about the protocol for about 5 minutes now 🙂 So from what I understand you have a master and a slave configuration. The master sends out requests which the slave node(s) reply to. Typically a polling scenario. In order to get data upon events I have to set up the PLC as a master which writes to the PC as a slave.

Library Overview This section outlines all objects that the library currently contains. G Series VFD Control – fbVFD_GSeries The G Series VFD Control Function Block is utilized for use of Siemens G Series VFD or Micromaster VFDs using Standard Telegram 1.

I am working one one project which needs to realise the Modbus RTU master function in C#, in order to read the data value from the slaves. I found that your library is the best, but.my problem is that: Can you explain to me the structure of your library? In fact I do not know which parts are the library excatly. It has so 6 projects when I open it in Visual C# 2010 some other I can not even open Thanks a lot.

I have no way to control this event handler from my code. I have tried to catch this exception, but haven’t been successful. This is a problem in my software because if the ModbusTcpSlave needs to be shut down and restarted (e.g., in the case of a communication failure), then when it is restarted and the master reconnects, then the original ports remain open. Eventually, those open (but now dead) ports are causing the software to crash.

Modbus Tcp Library

Its very feasible to write a custom protocol with FB50 and FB60. I was hoping someone else has been down this path and might have a working example to share. I really only need to implement a simple class 0 master or slave. The Open Modbus/TCP you describe has a few problems. It uses the AG_SEND and AG_RECV Siemens blocks, which in turn use SFC58 and SFC59. In any complete TCP/IP transaction, these limit the length of any transfered data to 240 bytes.

But when I run the same settings using same converter same device with Modbus RTU holding register read (start address = ushort 3901 and no of reg = ushort 2, device address = 1), my c# code throws an exception saying “Function code 131, exception code 2, the data address received in query is not an allowable address ”. For the time being this is beyond me, how come NModbus driver is interpreting the same working address as wrong? Anybody has any clue? Please drop me a line. Mesta u r very correct.

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