Siemens SIMATIC NET PROFIBUS - Manual (Page 88)

Configuring Networks
3-22
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000
3.3 Transmission Delay Time
The system reaction time of a PROFIBUS network depends largely on the
following:
S The type of system being used (single or multiple master system)
S
The maximum reaction time of the individual nodes
S
The amount of data to be transmitted
S
The bus configuration (topology, cable lengths, active network components)
The bus parameters are adapted (configured) to the particular PROFIBUS network
using configuration software such as COM PROFIBUS or STEP 7.
Using optical link modules, extremely large PROFIBUS networks can be created.
These allow the use of long optical fiber links and the cascading of large numbers
of components. Each time the data packet passes through an OLM there is a
delay.
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
transmission rate.