Configuring Hardware and Communication Connections STEP 7.pdf

Configuring the Distributed I/O (DP)
3.12.4 Shortening the Process Reaction Time by Overlapping Ti and To
If, in your configuration, you select DP slaves that allow overlapping of Ti and To,
you can then shorten the DP cycle and, with it, the process reaction time even
further.
For example, IM 153-2 (as of 6ES7 153-2BAx1) supports overlapping of Ti and To.
This has no influence on the selection process during configuration, since STEP 7
automatically determines the times and, based on the configuration selected,
calculates the shortest possible DP cycle time.
Please note the following for the configuration:
• In the tab "Constant Bus Cycle Time", deactivate the option "Times Ti and To
same for all slaves" and set these times for each slave.
• If modules using inputs as well as outputs are to be used in isochrone mode,
then overlapping Ti and To times are possible.
Overlapping Processing
The principle governing the overlapping of Ti and To functions as follows.
The peripheral input module is already reading the inputs while the peripheral
output module is sending the process reaction from the user program on to the
outputs.
Configuring Hardware and Communication Connections with STEP 7
3-92 A5E00706939-01