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jose7771

communication with modbus

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hi to all i am using s7, cpu type 226 with hmi ( touch panel 270 -10'') my plc will be integerated to dcs (client scope), using modbus protocol .please suggest me on how to interface with dcs both hardware and software and the addressing schemes ( coils , contacts, holding registers, and the relevant data), similarly as to how to map address into hmi regards jose

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You should use the add-on library that includes code for Modbus. It will allow you to perform Modbus SLAVE requests out the serial port. As for the hardware interfacing, you need to know if they are using Modbus RS232 or RS485 and what teir connection to the DCS system is. Check the manual for the S7-200 for the section on Modbus communications. You can download this manual from www.sea.siemens.com in their Micro Automation section

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the sir thanks for ur useful information which is really helpful to me ,i really appreciate it i have one more doubt , as to how to assign the modbus code and to interface with hmi and what will be acting as the master ( hmi tp 270 or dcs ) the dcs uses modbus RS 232, I have visited the website suggested by u but the page was showing some error .please help me out regards jose

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I'm adding the S7-200 Programming Manual to the download section. It's about 6 megs.

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Jose, I posted an attachment on another topic which I gave him code to be a modbus master. the library that siemens offers is only a modbus slave. please take a look at this topic and you can download the code. it is very well documented. Khek http://forums.mrplc.com/index.php?showtopic=1476

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