Siemens SIMATIC ET 200M Manual page 55

Configuration Options with the ET 200M
Prerequisites
S Interface module IM 153-2; Order number 6ES7 153-2Bx00-0XB0 as of E01
S STEP 7 V5.2 or higher
S PROFIBUS-DP must have a data transfer rate of at least 1.5 Mbaud (low
equidistance times can be achieved using high baud rates).
S The maximum equidistance cycle is 32 ms.
S The equidistance master must be a DP master of class 1, i.e. a PG/PC cannot
be an equidistance master.
S In equidistance mode, only one DP master (class 1) can be active on the
PROFIBUS-DP. PGs and PCs (class 2) can be connected additionally.
S The clock synchronism can only be activated at the ET 200M if the equidistant
bus cycle has been activated on the DP master system and at least one module
with synchronization support has been configured.
Optimizing the Equidistance Time
S The longest (parameterizable) delay for the digital input/output modules
determines the length of the equidistant DP cycle.
Tip: With clock synchronism, make sure that all of the digital modules in the
ET 200M station have the same delay.
S The smaller the input delays are that you set for the digital input modules, the
shorter the possible equidistance times will be.
Tip: Wherever possible, set an input delay of 0.1 ms for the digital input
modules.
S In the case of modules which support clock synchronism, the processing time at
the module must also be taken into consideration.
S The minimum possible equidistance times in the station depend on the number
of modules in the ET 200M.
You can also achieve small equidistance times if you distribute the modules of
an ET 200M (with a large number of modules) between two ET 200M stations.
S The equidistance time is reduced if you increase the baud rate.
Tip: Set the highest possible baud rate.
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Distributed I/O Device ET 200M
EWA-4NEB780600602-06