Siemens S7-300 appendix DP cycle times in the Profibus DP network, 17 ms

Cycle and reaction times 5.3 Response time

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.

Bus runtime

17 ms

7 ms

Transmission rate 1.5 Mbit/s

6ms

5ms

4ms

3ms

2 ms
						Transmission rate 12 MBit/s
1 ms
Minimum							Number of DP slaves;
slave interval
							maximum number is
1	2	4	8	16	32	64
							dependent on CPU

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	5-15
Manual, Edition 08/2004, A5E00105475-05