Functions
3.1 Cycle synchronization
IM151-1 HIGH FEATURE interface module (6ES7151-1BA02-0AB0)
20 Manual, 03/2008, A5E01075975-02
● In constant bus cycle time operation, the ET 200S requires a starting time of approx. 150
DP cycles to guarantee isochronous operation up to the terminals.
● The bus length must be less than 1 meter.
Note
Isochronous operation is only possible without interference frequency suppression and
without smoothing.
Optimizing the constant bus cycle time
● Ensure equal input delay of all the digital input modules in the ET 200S station for cycle
synchronization.
If the settings differ, the lowest input delay is used to calculate the DP cycle time.
Changes at the inputs of modules with a higher input delay are recorded with a
corresponding time offset.
This also applies to the digital output modules. Choose modules with the same
conversion time TWA here.
● The shorter the input delays you set for the HIGH FEATURE digital input modules, the
shorter the constant bus cycle times that can be achieved.
Hint: Set an input delay as close to 0.1 ms as possible for the HIGH FEATURE digital
input modules.
● The processing time of the modules should be taken into account in the case of modules
that support isochronous operation.
● The minimum constant bus cycle time depends on the number of modules in the ET
200S.
Hint: Always try to use 4-channel digital input HIGH FEATURE modules to reduce the
number of modules required.
Shorter constant bus cycle times can be achieved by distributing the modules of an ET
200S (with a high module count) over two ET 200S stations.
● The constant bus cycle time is reduced if you increase the transmission rate.
Hint: Set the highest possible baud rate.
● Interface module 151-1 HIGH FEATURE, 6ES7151-1BA02-0AB0 and higher: An
optimization of the periods for the constant bus cycle can be achieved through the correct
plugging sequence of the electronic modules:
– Plug the output modules with the longest processing time on the left in the ET 200S.
– Plug the input modules with the longest processing time on the right in the ET 200S.
The processing times (= TWE or TWA) can be found in the technical data for the module
concerned.
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