Product Information for Distributed I/O Device ET 200M, Manual
4
A5E00272208-01
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On Section 3.7
Further information on the jitter
The maximum jitter amounts to 10
µ
s if
•
The equidistance cycle of the DP master (pulse control at the PROFIBUS DP)
does not exceed a jitter of 1.3 *s and
•
only the IM 153-2Bx.. is regarded with PROFIBUS DP and I/O bus.
The jitter is not always observed when asynchronous events (e.g. withdrawing and
plugging, diagnostics) occur. It is possible to eliminate the influence of
asynchronous events on the jitter by configuring "Reserve periods".
Due to existing variety the jitter of the periphery (I/O) modules of the ET 200M
cannot be taken into consideration.
Further information on the properties
In case of asynchronous events (e.g. withdrawing and plugging, diagnostics and
interrupts of periphery (I/O) modules) the reaction of the of the IM 153-2 to the I/O
units can fail or a larger jitter can occur during a cycle.
Further information on the properties
If the ET 200M is operated at a non-S7 DP master, stable equidistant operation is
only ensured if the DP master fulfils the following requirements:
•
The DP master has to be configured with the "delayed" interrupt mode.
The data transfer is then not interrupted. A diagnostic message is inserted into
the next free time window for acyclic jobs.
•
The DP master has to operate with the repeat strategy "retry next cycle“.
The repetition of a message is then not carried out in the same cycle in which
the fault occurred, but rather in the following cycle.
•
The DP master has to support the modified Target Rotation Time process (in
accordance with IEC 61784-1:2002 Ed1 CP 3/1) for further active stations.
Otherwise asynchronous events (such as hardware interrupts, diagnostics) can
cause cycle failures or a larger jitter. These failures / larger jitters can always be
expected when the asynchronous events occur very often
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