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CP 341 COMMUNICATION PROBLEMS

Created by: introberg at: 10/2/2008 7:07 PM (3 Replies)

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10/2/2008 7:07 PM	Rate (0)
introberg Posts: 3 Rating: (0)	Hi dears, I need someone helpme, I have tried practicethe communication modbus rtu betwen CPU 315-2DP (master CP-341 RS422/485) and one slave modbus to begin, I've follow each step that manual "loadable driver for point -to-point CPs Modbus Protocol RTU Format S7 is Master" recommend and I've used the example called modma, such as it recommend, but not even I have send any data ( I mean, not even turn on green led TX). Please helpme. apologize for my poor english. best Regards
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10/3/2008 8:16 PM	Rate (0)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (309)	Hello, We need some info like error codes, diagnostic dat, ....to find out where the error may be located. Start may be with the following: - is the Modbus driver dongleinserted in the CP341? - is the driver loaded in the CP? - is the SF LED on or off - do you see any error in online mode in the HW Config? - do you see error codes at the outputs of the FBs? - are you sure about the cabling on the interface? See chapter 7 of this manual http://support.automation.siemens.com/WW/view/en/25362836
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10/5/2008 1:00 AM	Rate (0)
introberg Posts: 3 Rating: (0)	-the modbus driver dongle is inserted in the cp -the driver is loaded in the CP -the SF,TXD and RXDLEDS,are always inoff. -I don'tseesome error in online mode in the HW Config - when trigger REQof FB8 (means M127.0), inmediately increment errors counter and in the status outputshow the event class N° 0E44 - the cable interface is ok. the error 0e44 mean that the value of the transferred parameter "Amount of bits" is out of range (1-2040). I can't find where change this parameter, please helpme. bye
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10/5/2008 7:07 PM	Rate (0)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (309)	Hello, The solution for that type of error is "Correct your source DB". Or the LEN parameter also I would say. For FB8 (P_SND_RK ), depending on the function code, you must follow some rules. When P_SND_RK is activated, the source data area specified with the parameters DB_NO and DBB_NO is transferred to the CP with the length LEN. See for valid LEN at page 6.1 of themanual mentionned above. If the transferred data quantities differ from those listed above for the individual function codes, the job is not carried out and P_SND_RK rejects it with an edge at output ERROR. How the source data area must be filled in depends on the function code, see chapter 5. (the first byte is the slave address, the second byte of the data, followed by further data) What function code do you use? What is the LEN value? Did you filles in the data in the DB specified by DB_NO en DBB_NO?
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