User Manual

PROFIBUS DP/P-bus link Siemens Building Technologies
1-4 User's guide Building Automation
1.5 Cycle times of the DP/P-bus link
The cycle times depend on the number and type of DESIGO I/O modules connected.
The DP/P-bus link takes less time to process digital modules than it does to process analog
modules. With the latter, more time is required to convert the values into the format of the re-
ceiving device.
The cycle time also depends on the number of channels of a module. Here too, more time is
required for analog modules, as most of them have two or four channels.
For an average module mix, comprising 30 digital and 20 analog modules, the duration of one
cycle is approximately 350ms.
When calculating cycle times for the DP/P-bus link, remember to include the processing time of
the DP master CPU and the transfer time for the Profibus connection.