Example Of Configuring The Bus Parameters In Step 7 - Siemens SIMATIC NET PROFIBUS Owner's Manual

Configuring Networks
Note
The slot time calculation takes into account only the optical network and the
attachment of nodes to the OLM in each case via a maximum 20 m long RS-485
bus segment. Longer RS-485 bus segments must be included by adding them to
the length
FOC
With the OLM/G11-1300 and OLM/G12-1300, the minimum slot times shown in the
following table must be maintained at transmission rates of 12 Mbps, 6 Mbps, 3
Mbps and 1.5 Mbps.
Table 3-11
OLM/G11-1300 and OLM/G12-1300
Transmission rate
When configuring the slot time, use the minimum slot time as shown in Table 3-11
if the calculated slot time is less than the minimum slot time.
Note
If the slot time is configured with a value that is too low, this can lead to
malfunctions and error displays on the OLM. The system LED flashes red/green.
3.3.3

Example of Configuring the Bus Parameters in STEP 7

Structure of the Network Example
The example assumes a redundant optical ring with the following structure:
S 20 OLM G12 modules in the redundant optical ring
S 20 km total ring length
S Transmission Rate 1.5 Mbps
S Nodes attached directly to OLMs
S "PROFIBUS-DP" bus protocol
3-30
.
Minimum Slot Time for
12 Mbps
6 Mbps
3 Mbps
1.5 Mbps
Minimum slot
time
3800 t
Bit
2000 t
Bit
1000 t
Bit
530 t
Bit
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000