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Modbus RTU with CP341 RS232C

Created by: AhmetTan at: 8/6/2010 8:08 AM (2 Replies)

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8/6/2010 8:08 AM	Rate (0)
AhmetTan Experienced Member Joined: 3/17/2010 Last visit: 11/10/2023 Posts: 29 Rating: (0)	Hi, Excuse me to create a similar thread here, but I had to. I read lots of questions and answers on this forum, but the more I read the more I confused. I felt to ask with my words. I have a CPU 315 and CP341 RS232C (Order no:6ES7341-1AH02-0AE0) I have also TRIO 302 Motion controller for stepper. Trio supports Mudbos RTU protocol. I need to control stepper motor talking to Trio controller via Modbus. I have to write a value to a register in Trio and read from register. I don't have complicated conversation. I don't have detailed and experience knowledge about Modbus. So, sorry if I ask some simple questions. My questions: 1) Would RS232C complicate the things, would RS485 be better, or is it not relevant? 2) I read in so many threads here that Siemens sell "loadable modbus driver w/ dungle for CP341". Do I have to buy it to be able to talk to Modbus slave? 3) If I don't have to buy, There are 4 different protocol comes with CP341 config. package. 512K, 3964, ASCII and Printer. Which one should I choose? 4) If I can use one of the protocol above, would you guide me how to write a value to a register in Modbus slave device (Trio controller). I believe my project is simple, but need a sample to learn how to establish a Modbus. In this forum, I read some function blocks like FB7 FB8, or FB200 or some others. I am not sure what and how to use. Thanks for your help.

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8/6/2010 8:58 AM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 3/21/2025 Posts: 8904 Rating: (1187)	AhmetTan 1) Would RS232C complicate the things, would RS485 be better, or is it not relevant? When you have one slave, it is not relevant. When you have more slave's you should use RS485. AhmetTan 2) I read in so many threads here that Siemens sell "loadable modbus driver w/ dungle for CP341". Do I have to buy it to be able to talk to Modbus slave? When you want to use Modbus RTU as protocol, you need to buy Loadable driver and dongle. Unless you write your own driver. AhmetTan 3) If I don't have to buy, There are 4 different protocol comes with CP341 config. package. 512K, 3964, ASCII and Printer. Which one should I choose? None of them, when you want to use Modbus RTU. Or the mentioned slave can communicate through another protocol. AhmetTan 4) If I can use one of the protocol above, would you guide me how to write a value to a register in Modbus slave device (Trio controller). I believe my project is simple, but need a sample to learn how to establish a Modbus. In this forum, I read some function blocks like FB7 FB8, or FB200 or some others. I am not sure what and how to use. Perhaps this manual can help: SIMATIC S7-300/S7-400 Loadable driver for Point-to-Point CPs: MODBUS protocol, RTU format, S7 is master Best regards, Wizard
	Last edited by: Wizard at: 8/6/2010 9:01 AM
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8/6/2010 6:24 PM	Rate (0)
AhmetTan Experienced Member Joined: 3/17/2010 Last visit: 11/10/2023 Posts: 29 Rating: (0)	Thanks Wizard. Your answer helped a lot to clarify my concerns.

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Modbus RTU with CP341 RS232C

Created by: AhmetTan at: 8/6/2010 8:08 AM (2 Replies)

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Last edited by: Wizard at: 8/6/2010 9:01 AM

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