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modbus

Created by: girish bodhale at: 1/29/2014 7:53 AM (9 Replies)

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1/29/2014 7:53 AM	Rate (0)
girish bodhale Posts: 51 Rating: (1)	Hi, I have a s7-200, cpu224 PLC and Softlink USB\PPI Cable, I want to test this PLC for modbus communication So can any one help me out on, how do i communicate this plc and if possible which modbus tester do i use for the same
girish bodhale Posts: 51 Rating: (1)
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1/29/2014 12:44 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	What modbus protocol are you using? TCP ot RTU? Is the S7 a master / client or slave / server?
	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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1/29/2014 12:56 PM	Rate (0)
girish bodhale Posts: 51 Rating: (1)	RTU
girish bodhale Posts: 51 Rating: (1)
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1/29/2014 1:15 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Ok, but you have only answered one of my questions. Are you wanting to test a slave or master device?
	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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1/29/2014 1:34 PM	Rate (0)
girish bodhale Posts: 51 Rating: (1)	Actually Both Master & Slave As i mentoned earlier that i have 1) CPU 224 2) Softlink Cable (PPI) 3) Modbus Tester Beta v0.3 Am eager to see how this modbus protocall works So by using modbus tester i want to read and write values to/from plc
girish bodhale Posts: 51 Rating: (1)
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1/29/2014 7:34 PM	Rate (1)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 3/23/2025 Posts: 12344 Rating: (2707)	Hello girish; What your description implies is that your tester would be the master on Modbus RTU, and the S7-224a slave. Only the master can read/write on a Modbus network, the slave cannot initiate any exchanges. In any case, to setup Modbus RTU (either as slave or as master) on a S7-200 CPU you need to purchase a Modbus library for MicroWin. You will find the information in the FAQ below: Where in STEP 7 Micro/WIN can I find the operations libraries for the Modbus RTU protocol and USS protocol? The Modbus functions (available in your program once the library is installed) are described in this manual: S7-200 System Manual Hope this helps, Daniel Chartier .

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1/30/2014 10:53 AM	Rate (1)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	If it is PC apps for testing mobus interfaces on the S7 that you are wanting, I have both master and slave freeware apps that I can send you. Please PM me if you are interested.
	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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1/30/2014 3:03 PM	Rate (0)
girish bodhale Posts: 51 Rating: (1)	Thanks a lot for replying to my post What if i have a sample program including the required modbus instructions, but with no library function in it, will the communication be a sucess for the same i have attached jpg file please have a look at it. Attachment siemens.JPG (115 Downloads)
girish bodhale Posts: 51 Rating: (1)
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1/30/2014 6:22 PM	Rate (1)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 3/23/2025 Posts: 12344 Rating: (2707)	Hello girish; I have never tried it myself. My experience with Siemens (and most PLC manufacturers for that matter)is that if certain blocks belong to a licensed library you will have no way of running them without the correct license. However, just try dowloading the project to your CPU, report back to us on your results, it might be interesting one way or the other. Hope this helps, Daniel Chartier

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4/7/2014 1:02 PM	Rate (0)
CS Moderator Moderator Joined: 9/1/2005 Last visit: 3/10/2025 Posts: 4113 Rating: (195)	follow up question published bygirish bodhaleis split to a seperate thread with the subjectcable configuration to communicate this modscan software with cpu 224. 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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