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knowing the Modbus slave adress

2/10/2012 2:41 PM	Rate (0)
CSven Member Joined: 2/8/2012 Last visit: 10/15/2024 Posts: 2 Rating: (0)	automatizzando Hoping to please, I enclose an example of communication between Modbus TCP s7 1200 (master) and Zelio Logic (slave). I used a Zelio as a slave because it was the only device that modbus tcp aho available at this time. Joseph Attachment:Test Zelio modbus TCP (software per S7 1200).zip (56 Downloads) I have a problem with knowing what Modbus slave adress the Zelio has. Anyone who knows? Tried with 1 and 255.
	Last edited by: O_Moderator at: 2/13/2012 10:51 AM new subject after spliting from /tf/WW/en/Posts/65405#top Last edited by: Cswid at: 2/10/2012 4:53 PM
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2/15/2012 1:11 PM	Rate (0)
Kaulquappe Posts: 3093 Rating: (324)	Hello Cswid, most of the ModbusTCP devices use slave address 1, when it doesn't work i would try 0. But I don't really know it. Regards, Kaulquappe
Kaulquappe Posts: 3093 Rating: (324)
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2/15/2012 5:28 PM	Rate (0)
smiffy Platinum Expert Joined: 1/17/2007 Last visit: 3/10/2025 Posts: 1557 Rating: (540)	Do not try address 0. That is a special address reserved for broadcast requests (requests addressed to all slaves). Why do you not know the configured slave address? If it is your own hardware, it would be set somewhere in the hardware or configuration software for the device. If it is a 3rd party device, you could always ask them what the slave address is. They should know this. Failing that, there is no quick way of doing it. I could be any address from 1 through to 247 (it should not be higher than 247 as those addresses are reserved, but check them anyway in case they have not played by the rules). So you would have to check each address in turn until you get lucky. The trouble is, if you have not yet validated the interface, then there may be another issue whereby the slaves are not responding (other than wrong slave address), and the whole exercise of slave address searching may be futile. I suggest that you use a very simple request to do the slave address search, one that is almost guaranteed to work (e.g. read 1 register from the start of the data in the slave).
	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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