Two ET200iSP units chain connected

Dear experts,

I'm looking at the single line topology part from the attached capture(left side) .It is taken from a Siemens document.

The Remote I/O  is an ET200 iSP system.The blue line is a RS485 iS cable .The RS485 IS coupler acts like a network bridge between RS485 iS and Profibus DP.

The IM152,which is the ET200iSP CPU,has a RS485 iS interface and indeed you can connect two remote I/O units(ET200iSP) via RS485 iS  , but I can't possibly understand how can you connect the last remote I/O unit(ET200iSP) from the chain with the RS485 IS coupler since its interface is already used for the connection with the previous remote I/O unit (ET200iSP).

Can you guys please explain me how is this possible?

Additionally I would like to know if it's possible to have more than two ET200iSP units connected in a chain connection via RS485 iS cable as the figure suggests. 

Thank you.

Best regards

aney_312

Hello,

probably maybe don't understand exactly what you want know, but maybe answer is very simple  -

due RS485 multidrop capability?

Hi Darius_I,

Thank you for answer. 

The IM152 has one single RS485 port. The capture attached shows that it has 2 connections: one with RS485iS coupler and the other one with another IM152.

How can it have 2 connections since it's having one single port?

Best regards

aney_312

Hello aney;

The RS 485-IS coupler isolates the Profibus-DP busline from the DP-master from the RS 485-IS bus connecting the IM 152s.

Understand that the "RS 485-IS bus" is actually an intrinsically-safe Profibus line, and as such shares the configuration and parameterisation of Profibus networks. You can use the IM 152 even in Zone 1, with adequate Profibus connectors (see the attachment, taken from the following document):

https://support.industry.siemens.com/cs/ww/en/view/19767520

Notice the drawing in the attachment; it shows the IS Profibus connector in an open state, so you can see the cable connections. This is the same with any approved Profibus connector, IS or not: one cable coming in ( on connection points A1/B1«0, one cable going out to the next station (on connection points A2/B2). So daisy-chaining all the nodes on the Profibus line is very simple.

Once there is no further node on the bus (this is the last station) then there is only one cable entering the Profibus connector,  wired on A1/B1 connection points, and the termination resistor (a switch on the body of the Profibus connector) must be ON.

If you need further instructions or documents on Profibus, I suggest you go to the Profibus.com website, and download Installation Guides for Profibus-DP; there is specifically a Profibus Rs 485-IS User and Installation Guideline that would be very helpful in the same section; you could also look at the System Descriptions in the Technical descriptions and Books section, they are very well-designed and informative.

http://www.profibus.com/download/

Hope this helps,

Daniel Chartier

Hello Aney_312,

best will be to begin study RS485 basic principles, this theme will give you basic answer. Then you can proceed next with Daniel's post to study DP network systems,...

Hi DChartier,

Thanks.It has been a while since I haven't used profibus and I totally forgot that there is an extra extension cable in order to achieve the daisy chain connection with the third party RE485iS/PB device. 

Darius_I,thank you for your recommendation as well :).

Best regards

aney_312