Siemens SIMATIC S7-400H Manual page 129

Note
The addition or removal of interface modules IM460 and IM461, external DP
master interface module CP443-5 Extended and the associated connecting cables
is not allowed.
Adding or removing components of the remote input/output station, such as
– DP slaves with redundant interface module (e.g. ET 200M or PA link)
– one-way DP slaves (in any DP master system)
– modules in modular DP slaves
– PA coupler
– PA devices
Use of a free channel on an existing module
Changing certain CPU parameters
Changing the Memory Components of the CPU
With all modifications observe the rules for the configuration of an H station (see
Section 8.2.1).
What should I note at the system planning stage?
In order for switched I/O to be able to be expanded while in operation the following
points are to be taken into account at the system planning stage:
In both cables of redundant DP master system sufficient numbers of branching
points are to be provided for spur lines or dividing points (spur lines are not
permissible at transmission rates of 12 MBd). These may either be provided at
regular intervals or at all well accessible points.
Both cables are to be uniquely identified so that the line which is currently
active is not 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 excellent for this.
Modular DP slave stations (ET 200M) and DP-PA links are always to be built up
with an active backplane bus and fitted as fully as possible with bus units since
the bus units cannot be plugged in and unplugged while in operation.
PROFIBUS DP and PROFIBUS PA LAN cables are to be equipped with active
bus terminators at both ends so that the lines continue to be correctly
terminated during the modification work.
PROFIBUS PA bus systems should be built up using components from the
SpliTConnect product range (see interactive catalog CA01) so that separation
of the lines is not required.
S7-400H Programmable Controller Fault-Tolerant Systems
A5E00068197-04
Modifications to the System while in Operation
10-3