Installation and Maintenance
5.10 Configuration
SIMATIC NET PROFIBUS, Optical Link Module
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Operating Instructions, 07/2008, A2B00065774O, Edition V1.5
5.10
Configuration
Because of frame delays due to cables, network components and monitoring
mechanisms in the network components, the PROFIBUS network parameter "slot
time" must be adapted to the network span, the network topology and the data rate
when configuring the network.
5.10.1
Configuring optical bus and star topologies
You configure the PROFIBUS network, for example with SIMATIC STEP 7 (V5) or
COM PROFIBUS (V5). You enter the number of OLMs and overall cable length in
a configuration dialog. The configuration tools then check whether the slot time can
be retained in the chosen communication profile. If the limit is exceeded due to the
extra delays caused by OLMs and fiber-optic cables, a warning message is
displayed and the parameters are adapted.
5.10.2
Configuring redundant optical rings
The following configuration requirements must be met in the redundant optical ring
(see section 3.3 for details):
¾
One unused address lower than the HSA
(1)
¾
Increase of the retry value to at least 3
(2)
¾
Checking and adaptation of the slot time
(3)
Use the user-specific profile of the configuration tool to set the parameters under
(2) and (3). Calculate the slot time based on the following equation:
Slot time = a + (b * Length
FOC
) + (c * Number
OLM
)
Slot time
is the monitoring time in bit times
Length
FOC
is the sum of all fiber-optic cables (segment lengths) in the
network.
The length must be entered in km!
Number
OLM
is the number of the PROFIBUS OLMs in the network.
The factors a, b and c depend on the transmission speed and can be found in the
following table:
