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S7-1200 with PAC 3200 on Modbus TCP

Created by: thomash3 at: 9/20/2011 11:07 AM (11 Replies)

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9/20/2011 11:07 AM	Rate (0)
thomash3 Posts: 10 Rating: (0)	Hello, I'm trying to communicate PAC 3200 with S7-1200 with new block MB_CLIENT. PAC is working on MODBUS TCP protocoll (address 192.168.0.10). I've put MB_CLIENT block in OB1 like in attachement. Communication is probably OK, because there is no error, Status =0 (when cable is disconnected an error occurs, Status=7002). CPU doesn't read parrameters from PAC (MW10, MW12, etc. = 0). I think, that S7-1200 reads wrong registers from PAC (when I've tried read from MB_DATA_ADDR=1 or 10001 or 40001, I had this problem too). I am using: CPU 1212 AC/DC/RLY (FW 2.1) STEP7 BASIC V11 SP1 + UPD2 PAC 3200 (FW 2.2.0) What is the really reason? Please advice Best regards Thomash3 Attachment modbus_client.JPG (1415 Downloads)
thomash3 Posts: 10 Rating: (0)
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9/20/2011 2:09 PM	Rate (0)
hschaft Posts: 57 Rating: (8)	Try setting the attribute MB_Unit_ID to 1 on the MB_CLIENT. Although this value should not be necessary unless the slave module is RTU or the server is being used by a gateway. The PAC modules seem to need a value of 1 to 247. Hope this helps! If not, please post again.
hschaft Posts: 57 Rating: (8)
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9/20/2011 3:03 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Is data traffic being seen between the client and server? (use wireshark to check this). Is it just the data that is incorrect? The fact that you have no error code would suggest that the communications is working. It might be that the data is not correct or that you are requesting the wrong registers in the PAC. The address you are using (30001) and data length will try to read the first 10 "Input Registers" in the PAC. It is very difficult to say what the issue is without further information (a wireshark capture will help here).
	Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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9/20/2011 4:02 PM	Rate (0)
0_Einstein Diamond Member Joined: 7/7/2010 Last visit: 3/21/2025 Posts: 15745 Rating: (2489)	thomash3 Hello, I'm trying to communicate PAC 3200 with S7-1200 with new block MB_CLIENT. PAC is working on MODBUS TCP protocoll (address 192.168.0.10). I've put MB_CLIENT block in OB1 like in attachement. Communication is probably OK, because there is no error, Status =0 (when cable is disconnected an error occurs, Status=7002). CPU doesn't read parrameters from PAC (MW10, MW12, etc. = 0). I think, that S7-1200 reads wrong registers from PAC (when I've tried read from MB_DATA_ADDR=1 or 10001 or 40001, I had this problem too). I am using: CPU 1212 AC/DC/RLY (FW 2.1) STEP7 BASIC V11 SP1 + UPD2 PAC 3200 (FW 2.2.0) What is the really reason? Please advice Best regards Thomash3 Let me first say the things I think are correct to help you eliminate the them from thought. Inputs: [REQ, DISCONNECT, CONNECT_ID, IP_OCTETS1-4, IP_PORT] I do not know where the PAC 3200 MBTCP Server puts the values in modbus registers. Do you have a reference for that? If the PAC puts them in 30001-30010, then your other inputs are correct. On a crazy notion, is M0.0 toggling at 10 Hz? I assume so as you get an error when the cable is unplugged. Is there something in the PAC to enable MB TCP Server functionality and a configuration setting to tell it what data to store, and where to store it? Sorry I can't be of more help, but it looks like you have it right from the PLC side, assuming the PAC puts it in that address range.
	science guy
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9/20/2011 5:04 PM	Rate (0)
hschaft Posts: 57 Rating: (8)	Okay....I think I misread your question earlier today. When Modbus TCP Client is set to 1, 30001, 40001, the actual value that gets sent across the wire is 0x0000. However, the PAC monitor expects an address of 0x0001 for read of V1 Line. Therefore, you must put the MB_DATA_ADDR of the client to 40002 so that a 0x0001 will be transmitted. I do believe it is the same for all registers. The MODBUS TCP CLIENT addressing is based upon an offset of 0 as follows: MB_DATA_ADDR REQUEST ADDR SENT 40001 0x0000 400020x0001 40003 0x0002 while the PAC addresses are based uponand offset of 1 sothe first address of 0x0001 therefore your MB_DATA_ADDR has to be 40002, 30002, or 2 depending on what you are reading or writing. I hope that this answers your question.
hschaft Posts: 57 Rating: (8)
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9/20/2011 6:01 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Having looked at the PAC3200 spec, I concur with hscraft about the addressing. I wish vendors would use the correct addressing scheme and not the offset. The offset should only be used for the protocol layer. The applications layer should used the 00001, 10001, 30001 and 40001 addresses to prevent this exact type of confusion. Just a word of caution. The data is floating point (32-bit), so one value is spread over 2 modbus registers (16-bit) so you must always read an even number of modbus registers. If you do not, you will receive an error. The registers will also need converting back to real numbers once received. If you do not know how to do that, I can explain.
	Last edited by: smiffy at: 9/20/2011 6:02 PM Programming today is the race between software engineers building bigger and better idiot proof programs, and the universe producing bigger and better idiots. So far, the universe is winning...
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9/20/2011 7:48 PM	Rate (0)
thomash3 Posts: 10 Rating: (0)	Hello, Thanks to You all, the problem has been solved. There are two necessary things to establish connection and recieve data from PAC. Firstly, "MB_Unit_ID" has to be changed (for example to "1"). Secondly, "MB_DATA_ADDR" has to be 30002 (or 40002). My solution of conversion recieved data to real: I've been created a database with an 100 element-array of real. Then I've created pointer in MB_Client "P#DB2.DBX0.0 REAL 100". Variables are correctly displayed. Thank You all for help Best regards Thomash3
thomash3 Posts: 10 Rating: (0)	Last edited by: thomash3 at: 9/20/2011 7:58 PM
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This contribution was helpful to 2 thankful Users tomorrow nguyenminhdung120...

9/20/2011 10:43 PM	Rate (0)
0_Einstein Diamond Member Joined: 7/7/2010 Last visit: 3/21/2025 Posts: 15745 Rating: (2489)	That's good news!
	science guy
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9/27/2012 4:36 PM	Rate (0)
Rolf I4L Posts: 2 Rating: (0)	thomas,I have the same configuration, but it won't run. Can you send me you application or help me out? Thanks in advance.
Rolf I4L Posts: 2 Rating: (0)
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9/27/2012 5:06 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Hello Rolf, which error do you get? Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)
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