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S7-1200 Modbus Problem

Created by: Shahien at: 12/21/2013 9:18 AM (9 Replies)

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12/21/2013 9:18 AM	Rate (0)
Shahien Posts: 25 Rating: (3)	Hi Experts, I 'm trying to make Modbus (RTU)communicationby using s71200. I'm using CPU 1214C DC/DC/DC, CM 1241 (RS422/485) I'm lookingto read andwrite word registers in Load Cell Module connecting by Cm 1241 Rs422/485. I'm trying for a long time to make communication between Cpu 1214 Dc/Dc/Dc as master and load cell module as slave but Done of MB_Master block respond to me as false and error also is false!!! comm. cable connection (Rs485) Txd+ : pin3, Txd- : pin8 I attached my simple program. Please I'm lookingto help me to find where is the wrong in my simple program?!! Thank you Attachment CM Test.zip (421 Downloads)
Shahien Posts: 25 Rating: (3)	Last edited by: O_Moderator at: 12/24/2013 11:20 AM files transferred to attachment
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12/21/2013 1:41 PM	Rate (1)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (309)	Hello, You use the EN input of the MB_MASTER block. The same signal is used for the EN, and for the REQ input as a pulse. I wonder if this could be a problem that the FB will therefore never see a rising edge on the REQ input. The DONE and ERROR outputs also deliver a "1" value for one cycle (and of course only if you run in the FB). If you just look to the status of these signals via online functions, you must be very lucky to see them change to "1". Please try the changes in the document in annex. - I have suppressed the EN - I reset the request when done or Error came up - I count the done signals - I save the status in a status memory word, to be able to see the last error code You read registers 1 and 2 from the slave 5. Be sure the really are available in that slave. May be the slave has other register numbers Attachment Main (OB1).pdf (467 Downloads)
	Best regards jklm Suggestion was helpful? Feel free to rate it.
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This contribution was helpful to 1 thankful Users Shahien

12/22/2013 6:13 PM	Rate (0)
Shahien Posts: 25 Rating: (3)	Thanks Jklm for your consideration I executed the prog. Then, I found error code 808c and I solved the problem Thanks :)
Shahien Posts: 25 Rating: (3)
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This contribution was helpful to 1 thankful Users Kaulquappe

1/5/2014 8:48 AM	Rate (0)
Shahien Posts: 25 Rating: (3)	I solved the problem in my program Any one need help or informations about Modbus RTU protocol tell me and I will try to solve the problem
Shahien Posts: 25 Rating: (3)
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This contribution was helpful to 1 thankful Users S_Moderator

1/20/2014 5:44 PM	Rate (0)
Peter cowman Posts: 10 Rating: (0)	please help check out this thread V12 SP1 S7-1200 MODBUS RTU (485) MASTER PROBLEM Regards Pete
Peter cowman Posts: 10 Rating: (0)
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6/30/2014 1:24 PM	Rate (0)
CS Moderator Moderator Joined: 9/1/2005 Last visit: 4/10/2025 Posts: 4113 Rating: (195)	follow up question published byfaraz@6is split to a seperate thread with the subject S7-1200 Modbus Problem - communication with modscan simulator it doesnt work. Best regards CS Moderator
	My Forum is the place to personalize your profile, track your topics, and maintain content that interests you. Best regards CS Moderator
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7/7/2014 3:50 PM	Rate (0)
Narrator1 Bronze Member Joined: 3/25/2013 Last visit: 4/7/2025 Posts: 176 Rating: (1)	New question split intoconnect weighing indicators (mettler make IND331) to s7-1200 plc through CM 1241 RS422/485 module. With best regards, Narrator1

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8/7/2015 2:15 PM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by tuannguyenvan is split to a separate thread with the subject Communication between S7-1200 and the weghing indicator via rs485. Best regards Min_Moderator

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12/15/2015 8:05 PM	Rate (0)
Ertek68 Advanced Member Joined: 12/13/2012 Last visit: 9/16/2024 Posts: 13 Rating: (0)	Shahien I solved the problem in my program Any one need help or informations about Modbus RTU protocol tell me and I will try to solve the problem Dear Shahien; Please; share your project here. I want, S7 1200 communication with a Delta VFD-EL AC drive. This is my first project. But; I do not have much information about it.

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3/8/2016 11:31 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by Ygor0191 is split to a separate thread with the subject CPU 1214C communicate with a SEL 751A Relay. Best regards Min_Moderator

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