Assigning The Parameters For Cycle Synchronization On The Profibus Dp - Siemens Simatic ET 200S Operating Instructions Manual

Functions
7.2 Cycle synchronization on the PROFIBUS DP
Optimizing the constant bus cycle time
• The longest delays for the digital input/output modules (assignable in the case of inputs)
• The shorter the input delays you set for the HIGH FEATURE digital input modules, the
• The processing time of the modules should be taken into account in the case of modules
• The minimum constant bus cycle time depends on the number of modules in the
• The constant bus cycle time is reduced if you increase the transmission rate.
Further information
Further information pertaining to cycle synchronization can be found in the online help
function of
7.2.2

Assigning the parameters for cycle Synchronization on the PROFIBUS DP

Procedure
1. CPU settings:
Figure 7-1
7-4
are the critical factor in determining the length of the constant DP cycle. Hint: Pay
attention to equal input delay of all digital modules in the ET 200S station for cycle
synchronization.
shorter the constant bus cycle times that can be achieved. Hint: For the digital input
modules HIGH FEATURE, if possible, set an input delay of at least 0.1 ms.
that support isochronous operation.
ET 200S. Hint: Use at least 4-channel digital input modules HIGH FEATURE to reduce
the number of modules.
Lower constant bus cycle times can be achieved if you distribute the modules of an
ET 200S (with a high module count) over two ET 200S stations.
Hint: Set the highest possible baud rate.
STEP 7
and in the
"Object properties" of the CPU > Register "Cycle synchronization alarms"
– CPU - Set cycle synchronization alarm
– Select the DP master system used
– Select the desired sub-process image
Dialog box cycle synchronization alarms
Cycle Synchronization
manual.
Operating Instructions, 12/2005, A5E00515771-03
ET 200S