Siemens SIMATIC NET PROFIBUS Betriebsanleitung PDF herunterladen (Seite 18)

Network Topologies

3.3 Ring Topology

SIMATIC NET PROFIBUS Optical Link Module OLM V4.0

12 Operating Instructions, 01/2013, C79000-G8976-C270-03

If one module fails, only the DTEs connected to this module or the RS-485 segment are

disconnected from the ring. The rest of the network itself stays functional as a bus. The

problem is indicated by the LEDs of the two OLMs connected to the disrupted fiber-optic link

and by the signaling contacts of these OLMs. The segmentation is canceled automatically as

soon as both modules recognize that the segmented fieldbus (sub)network is no longer

disrupted based on test frames that they send out automatically. The bus then closes again

to form a ring.

Please note the following:

For correct operation, the following conditions must be met:

 Only use this mode, if you only connect PROFIBUS OLMs with at least version V3 with

each other. Both optical channels must be set to the “redundant optical ring” mode on all

PROFIBUS OLMs. All modules within a ring must be connected to each other over fiber-

optic cables. There must be no RS-485 bus cable within the ring.

 The MIN TSDR parameter described in the PROFIBUS standard EN 50170 /2/ must be

set to a value ≥ 11 on all DTEs. This is usually the case but should be checked if

permanent communication problems occur.

 Choose bus node addresses as low as possible when configuring your network, to reduce

master timeouts that may occur due to disruptions.

 If there is a failover (for example due to a cable break), there is failover time during which

correct data transmission is not possible. To ensure bumpless bridging for the application,

it is advisable to set the frame retry number on the PROFIBUS master to at least 3. To

ensure a bumpless return from the optical bus to the optical ring once a problem has been

eliminated, there must be no frame on the network at this time. This status occurs when

the master sends a GAP query to an address lower than HSA. The master tries to address

the device cyclically and waits for a reply at the longest until the configured slot time has

elapsed (“GAP query”). The OLM recognizes this status and closes the optical bus to

form an optical ring in the middle of this query sequence. This results in the following two

important configuration requirements for the redundant optical ring:



The val

ue of the parameter HSA (Highest Station Address) must be set on all DTEs

so that there is at least one address between bus address 0 and the value HSA that is

not occupied by a bus node, in other words there is at least one address gap. You can

create this address gap simply by setting the HSA value one higher than the highest

existing bus node address.

Notice

If this requirement is not or no longer met, the optical bus will no longer close to form

a redundant optical ring after segmentation. In this case the error message (LED and

signaling contact) of the two affected OLMs will not be cleared after eliminating the

problem.

 The slot time must be set to about twice the value compared with a not redundant

network. See section 5.10 for further information. You will find information on

cha

nging the setting in the documentation supplied with your DTE or with the

configuration software.

Notice

No glass fiber-optic cable may be connected to an OLM that uses plastic fiber-optic cable

and vice versa.

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 63 64

Kommentare zu diesen Handbüchern

Keine Kommentare

Siemens SIMATIC NET PROFIBUS Betriebsanleitung Seite 18

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Vernetzung Siemens SIMATIC NET PROFIBUS