5/16/2017 12:38 PM | |
Posts: 79 Rating:
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Hi to all, according to example programs on forum I made program for Modbus communication for slave S1200 (6ES7 214-1AG40-0XB0) and communication board CB1241 (6ES7 241-1CH30-1XB0) using TIA (Version V13 SP1 Update 9). In order to test communication I used second PLC as Master, and everything WORKED well. (parts of program for MODBUS communication can be found in attachment) Now, I want to test communication additionally with Modbus poll software on PLC. I am using Moxa 1150 with DB9 connector to connect PLC with PC. (wiring can be found in attachment) Settings of Modbus poll software can be found in attachment. When I use function code 03, TxD and RxD on Moxa connector are blinking, but only RxD is blinking on CM1241, and I receive error "Checksum error" when trying to write on only one address. Or "Insufficient bytes received" when trying to read from more then one address. When I use function code 06(write single register) I don't have errors but I don't receive anything on PLC. Also, I tried to change in Modbus poll to PLC address(base1) but received same errors. Can you please give me some advice? If anything else is needed let me know so I will post it later. Regards AttachmentModbus poll testing.zip (417 Downloads) |
5/17/2017 3:50 PM | |
Posts: 79 Rating:
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Anybody? Or if someone could give me program example, previously tested with Modbus poll software. Thank you in advance. |
5/18/2017 10:35 AM | |
Posts: 79 Rating:
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I feel like talking with myself, but I will keep talk :D From attachment below it can be downloaded program example from this forum, MODBUS communication between this two PLCs is working perfectly, but when I connect my PC to SLAVE PLC and try to test it with Modbus poll I receive errors like described in first post. Please give me some advice. Thank you AttachmentMODBUS test.zip (290 Downloads) |
Last edited by: Min_Moderator at: 5/18/2017 11:58:06 AMUpload attachment |
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5/23/2017 1:39 PM | |
Posts: 79 Rating:
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Dear Duris, thank you for your answer. In attachment you can find new photos of testing with Simply Modbus software. I think the problem is with expected response bytes. When I try to read 10 registers (20 bytes) expected response bytes is 25, as you can see on picture. I don't know for what are these 5 additional bytes? I hope this will help to find a problem. Regards Kijo AttachmentSiemens MODBUS problem.zip (288 Downloads) |
5/24/2017 9:35 AM | |
Joined: 4/28/2015 Last visit: 2/7/2024 Posts: 10533 Rating:
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Hello, look to www.simplymodbus.ca for byte sequence description, also you have that in SW. Look, logically 20 bytes are only your needed 10 values but MB complete message must also include other needed informations that are described in help. Pay attention to not manipulate with standard settings in PC SW (offsets) if you don't know really what you do. This can be not easy then recreate back to functional state. |
With best regards... |
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5/31/2017 9:36 AM | |
Posts: 79 Rating:
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Hi again, Regards Kijo AttachmentSlave.zip (240 Downloads) |
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