Siemens SIMATIC S7-400H System Manual page 284

System modifications during operation
17.2 Possible hardware modifications
What should I consider during system planning?
For switched I/O to be expanded during operation, the following points must be taken into
account already at the system planning stage:
● In both cables of a redundant DP master system, sufficient numbers of branching points
● Both cables must be uniquely identified so that the line which is currently active is not
● Modular DP slave stations (ET 200M), DP/PA links and Y links must always be installed
● Always terminate both ends of PROFIBUS DP and PROFIBUS PA bus cables using
● PROFIBUS PA bus systems should be built up using components from the SpliTConnect
● Loaded data blocks must not be deleted and created again. In other words, SFC 22
● Always ensure that the current status of the user program is available as STEP 7 project
Modification of the hardware configuration
With a few exceptions, all elements of the configuration can be modified during operation.
Usually configuration changes will also affect the user program.
The following must not be changed by means of system modifications during operation:
● Certain CPU parameters (for details refer to the relevant subsections)
● The transmission rate (baud rate) of redundant DP master systems
● S7 and S7 H connections
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are to be provided for spur lines or isolating points (spur lines are not permitted for
transmission rates of 12 Mbit/s). These branching points can be spaced or implemented
at any points that can be accessed easily.
accidentally cut off. This identification should be visible not only at the end points of a
line, but also at each possible new connection point. Different colored cables are
especially suitable for this.
with an active backplane bus and fitted with all the bus modules required wherever
possible, because the bus modules cannot be installed and removed during operation.
active bus terminating elements in order to ensure proper termination of the cables while
you are reconfiguring the system.
product range (see interactive catalog CA01) so that separation of the lines is not
required.
(CREATE_DB) and SFC 23 (DEL_DB) may not be applied to DB numbers occupied by
loaded DBs.
in block format at the PG/ES when you modify the system configuration. It is not enough
to upload the user program back from one of the CPUs to the PG/ES or to compile it
again from an STL source.
System Manual, 03/2012, A5E00267695-11
S7-400H