Dear All,

 i need some clarification on below points on segment length of communication protocol.

Here am not interested in the limitation of number of nodes.

1. In profibus maximum segment length without repeater.

Consider example of 12Mb/s. As per this speed, maximum segment length is 100 meter. So is it the distance between 2 node (not repeater) or total length between all the nodes?

2. In profinet it is mentioned as maximum distance of 2 partner is 100m. Also in the note it is mentioned maximum segment length. So which is referred as maximum segment here? between node or total length of all the nodes ?

3. Say node to node is 100m. So node can be anything. CPU, HMI, DRIVE etc. ?

4. If i need to do PLC-PLC communication over profinet also I should follow 100m distance rule between CPU ?

5. Distance limitation for RING TOPOLOGY ON PROFINET will remain same as PROFINET ?

Documents am referred attached..

 Hello vipz;

Let's see if we can clarfy your interrogations about network segments a bit.

Note that the definition of a "segment" will be different for different networks, based on the physical caracteristics of the support wiring: copper/optic fiber (multimode, singlemode, plastic, glass), RS-485/Ethernet, etc,,,

And in some cases you should be interested in the limitation of number of nodes...

1. In Profibus, the support wiring and electronics (over copper) follow RS-485 recommendations, and a segment is defines as (1) a maximum of 32 nodes (or 31 nodes + a repeter) or (2) a maximum distance at a precise bus speed (e.g. 100 m @12 MB), whichever limit applies first. So if you set the bus speed at 12 MB and have only a CPU master with one slave you can¸connect them with a length of Profibus cable of 100 m. max. Or if you reach 32 nodes over a distance of 50 m. at 12 MB you need a repeater (and a second segment) to go further distance.

2. Profinet (over copper) follows the design of Ethernet; all Ethernet networks over copper require a hub/switch after 100 m, no matter how many nodes are present. 

3. A node is simply a partner on the network. Wheteher you need  it to be master or slave(s) or IO device or any other specification of the node will depend on the protocol you want to use.

4. Profinet is Ethernet-based, so the 100 m rule applies to whatever configuration you design over copper.

5. The distance for a Profinet ring topology does not  follow segment lengths so much as switching times on the ring; redundant ring switching times  are determined using MRP (media redundancy protocol) and MRPD (Media Redundancy for Planned Duplication) protocols. You should look at the following Design Guide for more information:

PROFINET Design Guideline - Profibus.com

http://www.profibus.com/nc/pi-organization/regional-pi-associations/belgium/downloads/downloads/guidelines-1/download/10707/

Look at this similar document fro Profibus-DP topologies:

Profibus design and Good practices -Profibus International

http://www.profibus.com/uploads/media/03_PROFIBUS_Design_good_practices.pdf

Hope this helps,

Daniel Chartier