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Modbus TCP/IP

Created by: Ugljesa at: 8/21/2014 8:59 AM (6 Replies)

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8/21/2014 8:59 AM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 3/5/2025 Posts: 102 Rating: (1)	Dear experts, Few months ago I created program that alows data exchange between S7 1200 and Sentron Pac. In one single call of instruction MB_SLAVE I was able to read 120 registers from Sentron. Now, I need to communicate with Sepam S80 from Schneider. It seems like I can't "pool out" more than 3 registers in one call. What can be the problem? As far as I know, Modbus is standardized protocol. Any suggestion would be more than a helpfull. Thank you in advance, Ugljesa.

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8/21/2014 9:48 AM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Hello Ugljesa, which error do you get when you try to read more than 3 registers? Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)
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This contribution was helpful to 1 thankful Users Navnag

8/21/2014 12:08 PM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 3/5/2025 Posts: 102 Rating: (1)	There are no errors, just high level on Busy output.

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8/21/2014 12:23 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Hello Ugljesa, it is always the same, you can read it in several posts here in the forum: The outputs are displayed dynamically, they are only available for one cycle. So you must evaluate them in the program. You can't watch them in the variable table. Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)
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This contribution was helpful to 1 thankful Users Navnag

8/21/2014 1:04 PM	Rate (0)
Navnag Platinum Expert Joined: 11/21/2007 Last visit: 3/16/2025 Posts: 2326 Rating: (309)	Ugljesa Dear experts, Few months ago I created program that alows data exchange between S7 1200 and Sentron Pac. In one single call of instruction MB_SLAVE I was able to read 120 registers from Sentron. Now, I need to communicate with Sepam S80 from Schneider. It seems like I can't "pool out" more than 3 registers in one call. What can be the problem? As far as I know, Modbus is standardized protocol. Any suggestion would be more than a helpfull. Thank you in advance, Ugljesa. Hello As per the Manual of Modbus_TCP_for S7-1200 The Limit on No of Registers is : Read Input Registers / Holding Registers : 125 Registers Write Holding Registers : 123 Registers so there should no no issue regarding the no of registers as far as Modbus TCP Communication using S7-1200 is concerned. Problem could lie in the implementation of the logic or at the partner end. I would suggest that you have a re-look at your logic and if needed use a Modbus TCP Protocol tester ( e.g. MBPOLL ) to check where the problem lies. Hope this helps Cheers Navnag
	Last edited by: Navnag at: 8/21/2014 1:05 PM Last edited by: Navnag at: 8/21/2014 1:05 PM Typos corrected. There is no such thing as the last bug in a program There are no stubborn bugs, There are only stubborn Debuggers.
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This contribution was helpful to 1 thankful Users Ugljesa

8/21/2014 10:37 PM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 3/5/2025 Posts: 102 Rating: (1)	I'm sorry, but I think that I didn't understand you correctly. I'm using Data block for storing data from Sepam. Variable is array of real.
	Last edited by: Ugljesa at: 8/21/2014 10:42 PM
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8/21/2014 10:38 PM	Rate (0)
Ugljesa Bronze Member Joined: 10/29/2012 Last visit: 3/5/2025 Posts: 102 Rating: (1)	Thank you for your reply, I'll try to use Modbus tester.

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