Siemens SIMATIC NET PROFIBUS Instrucciones de operaciones descargar pdf (Pagina 15)

Network Topologies

3.1 Linear (bus) Topology

SIMATIC NET PROFIBUS Optical Link Module OLM V4.0

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

3.1.1 Linear (bus) topology with fiber-optic link monitoring and segmentation

Use this mode especially when you want a disrupted fiber-optic cable segment to be

separated from the rest of the network (see section 4.2.2.4). Only use this mode, if you only

connect PROFIBUS OLM V4.0 or V3/V4.0 with each other.

Monitoring mechanisms:

• Send echo: yes

• Monitor echo: yes

• Suppress echo: yes

• Monitor: yes

• Segmentation: yes

In this mode, the individual fiber-optic links are monitored by the two connected modules.

If a module fails or a fiber-optic cable breaks or disturbances are detected on the optical

transmission line, the fiber-optic link between the two OLMs is interrupted (segmented). The

PROFIBUS network is separated into two (sub)networks each remaining functional on its

own. The problem is indicated by the channel LEDs changing to red and by the signaling

contacts of the two OLMs connected to the disturbed fiber-optic link. 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.

Note that if a problem occurs in networks with several active bus nodes, two logical token

rings are formed. As a result, temporary network disturbances may occur due to double

tokens or frame collisions when the full network is restored.

Note:

If modules with two optical channels are used at the end of a line, the unused optical channel

must be set to the mode “bus without fiber-optic link monitoring”, so that it does not cause a

broken fiber-optic cable signal (see section 4.2.3.4). Remember that the optical channels

that are not connected must be protected against external light and pollution by protective

caps.

3.1.2 Bus topology without fiber-optic link monitoring

Use this mode when you connect a PROFIBUS OLM with a different fiber-optic component

according to the PROFIBUS guideline (optical/electrical converter), which does not send a

frame echo and does not expect or tolerate a frame echo.

Monitoring mechanisms:

• Send echo: no

• Monitor echo: no

• Suppress echo: no

• Monitor: no

• Segmentation: no

In this mode, there is no monitoring of the individual fiber-optic links.

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