Automatic assignment of DP slave station addresses.

Hi there fellow forum members.

Until now I have always assigned the Profibus Station address of slaves by setting the little DIP switches on the slave modules.
Collegue of mine now asks me why not just set the slave modules to auto.

I wonder if there are any problems or pitfalls. I find it a mystery how the slave or the master knows which station is which.

Questions:

If there are 2 DP slaves exactly the same, how are the right station numbers assigned to the right slaves ?

Is it the order that DP slaves are powered up that decides which slaves gets what station address ?

Is the station address somehow stored on the DP slave ?

In Vacon (Cuttler Hammer) VFD's, PB-address is parameter as nominal Current of the Motor. Parameter Default value is 126.

Errr... thanks seppo.

What I mean is: Some DP slaves can accept that they get their Station address from the master, rather than being set by DIP switches or in a parameter setting in a VFD.

Where/how do you set the slaves to auto ?

LD, that was the question I should have asked myself. When trying to find that piece of information, all is revealed.

It seems my collegue has gotten me started on a wild goose chase.
It appears that it is possible with a DP/DP Coupler only. Not with regular i/o such as ET200S.
My collegue still insist it is possible with ET200S, but the manual is quite clear to my opinion. He will bring some notes tomorrow. We shall see then.

And with a DP/DP Coupler it works so that you have to commision one DP/DP Coupler at a time, and the Station address is then stored in flash memory on the DP/DP Coupler.
I cannot really see any advantage with doing it like that. If I have 2 DP/DP couplers, and I sit in a remote control room trying to set the DP address on both DP/DP couplers, how can I know I am setting the DP address to the correct DP/DP coupler ?
As I see it, someone has to go onsite to switch them on one-by-one, and then I could just have set the address by the switches anyway.

Luckily, I've found my geese already:

That Looks like Harrold - Odell Country Park? Now I know where to find your wild geese, I think mine are in Martin Mere wetlands reserve.

There are some DP slaves that have no dip switches for address setting. To set the address you connect up to them with some profibus cable then assign the address from Simatic Manager - PLC, Profibus, Asign PROFIBUS Address.

Not sure about the auto bit? Is somone getting confused with ASi bus; that can auto assign addresses to a new slave but only if it is the only slave missing from the network.

Nick

Just a random Google image.

And from maintenance point of wiev, its easier when addresses have been assigned by dip switches.

Some profibus slaves can have their addresses set programatically, Simocode Pros for instance. However I have not actully tried to implement this. The last conversation I had with Siemens Tech Support on the matter was "if you get it working we would be very interested to know how you did it". It should be possible to detect a default DP address i.e. 125 and then send it a missing DP address for Faulty Device Replacement but as I said, I have not tried it. If your device has dip switches then it is not possible. You need to send a value acyclically to the register containing the DP address value.

Just a small correction.

JohnW said:

If your device has dip switches then it is not possible.

Click to expand...

Except for the DP/DP Coupler. It has dip switches for the station address, and one dip switch to select if the station address is set on the dip switches or by download via Profibus.