Configuration; Configuring Optical Bus And Star Topology; Configuring Redundant Optical Rings - Siemens SIMATIC NET Operating Instructions Manual

7.2

Configuration

Due to the delays caused by cables and network components and the 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.
7.2.1

Configuring optical bus and star topology

The PROFIBUS network is configured, for example, in SIMATIC STEP 7 (V5 or higher),
SIMATIC STEP 7 Professional (V12 or higher) or COM PROFIBUS (V5). You enter the
number of OLMs and overall cable length in a configuration screen. 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.
7.2.2

Configuring redundant optical rings

The following configuration requirements must be met in the redundant optical ring (see
section "Ring topology (Page 59)" for details):
● One unused address lower than the HSA (1)
● Increased retry value to at least the value 3 (2)
● Checked and adapted slot time (3)
To set the parameters in (2) and (3), use the user-specific profile of the configuration tool.
The following section describes how to calculate the slot time.
Calculating the slot time
Calculate the slot time according to the following formula:
Slot time = a + (b * Length
Slot time
Length
Number
Factors a, b and c
The factors a, b and c depend on the transmission speed.
Note
Remember the minimum slot times for OLM / G11-1300 and OLM / G12-1300.
Optical link module
Operating Instructions, 01/2020, C79000-G8976-C270-06
) + (c * Number
FOC
Monitoring time in bit times
Sum of all fiber-optic cables (segment lengths) in the network.
FOC
The lengths must be specified in km.
Number of PROFIBUS OLMs in the network
OLM
)
OLM
Planning/configuring
7.2 Configuration
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