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| 1/21/2013 3:32 PM | |||||||
Joined: 9/27/2006 Last visit: 3/23/2025 Posts: 12344 Rating:
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Hello Georgeous; 2 questions: - how many Modbus RTU slaves do you plan to connect to? 9 different slaves with RTD output, or one slave with 9 RTD channels? The question is whether you will use RS-232 (1 single slave) or RS-485 (up to 31 slaves); the type of CP 341 (give us the model number you are using) will determine what interface you can use. Or see the following table:
- to use Modbus RTU on a CP 341 you need a Siemensloadble driver, sold separately, and an associated hardware dongle that you will install on the CP 341 (it comes with the driver). This manual will give you an idea of what you need to purchase and how you can program the data exchanges: SIMATIC S7-300/S7-400 Loadable Driver for Point-to-Point CPs: MODBUS protocol, RTU format, S7 is master When you have decided to go ahead with the loadable driver, there are many interestoing posts that have been discussed on the forum, start by using the search box on the right of this page to look for threads and FAQs. Hope this helps, Daniel Chartier |
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Last edited by: dchartier at: 1/21/2013 3:45 PM |
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| 1/22/2013 1:32 PM | |
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Posts: 84 Rating:
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Georgeous U need to install the driver, then onvce you are going to hardware configuration, a Tab will be apear, and you can do some setting for the Module then you double click and load the driver, for loading the driver you need to stop the CPU, the your Module will work fine Also for programming you need to use some pulse signal for sending the packet and wait for reciving one, or else, if you have many devices which are connectedto one modbus link, you should send the packet ( including slave add. function code, start register and amount of data), to specific device, wait for a moment, if you get error or values, then send the packet to another device, ( with same or different configuration) nad repeat the whole cycle. U can use sample by Siemens, once you install the driver, samples also will be placed in project directory. Good Luck
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| 1/22/2013 2:26 PM | |
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Joined: 9/27/2006 Last visit: 3/23/2025 Posts: 12344 Rating:
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Hello Georgeous; You need a driver to implement any type of protocol on communication equipment. Each driver is specific for the type of data exchanges uyou need to do, and it is not so easy to write, test and make robust, especially for commercial or industrial applications. The Modbus driver you have purchased links the program blocks you insert in your program to the physical interface of the CP you are using, and formats all data exchanged to the protocol requirements. Without the protocol driver for Modbus RTU master, you cannot use the CP 341 as a Modbus RTU master. So your choices are limited to thiese: purchase the Modbus RTU protocol driver from Siemens and implement it as it has been written; locate a third-party protocol driver from an external source (they exist, but are not supported by Siemens, which means that your system will no longer recieve support in case of problems or damage); or write (develop) your own. See smiffy's comment in the following discussion about using a CP 340 as a Modbus master (Siemens provides no proptocol driver for Modbus on the CP 340): /tf/WW/en/Posts/45393#top |
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| 1/22/2013 2:32 PM | |
Joined: 1/21/2013 Last visit: 11/20/2024 Posts: 4620 Rating:
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Hi Georgeous, |
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