Siemens Simatic S7-300 Technical Data Manual page 97

DP cycle times in the PROFIBUS DP network
If you have configured your PROFIBUS DP master system in STEP 7, STEP 7 calculates the
typical DP cycle time to be expected. You can then view the DP cycle time of your
configuration on the PG.
The figure below gives you an overview of the DP cycle time. In this example, let us assume
that the data of each DP slave has an average length of 4 bytes.
With multi-master operation on a PROFIBUS-DP network, you must make allowances for the
DP cycle time at each master. That is, you will have to calculate the times for each master
separately and then add up the results.
CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
Bus runtime
17 ms
7 ms
6 ms
5 ms
4 ms
3 ms
2 ms
1 ms
Minimum
slave interval
1 2
Transmission rate 1.5 Mbit/s
4 8 16 32
Cycle and reaction times
5.3 Response time
Transmission rate 12 MBit/s
Number of DP slaves;
maximum number is
64
dependent on CPU
5-15