Configuring
4.6 Distribution of modules to several racks
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
4-9
Rules: arrangement of the modules on several racks
Please note the following points if you wish to arrange your modules on multiple racks:
• The IM always uses slot 3 (slot 1: power supply module; slot 2: CPU, slot 3: Interface
module)
• It is always on the left before the first signal module.
• No more than 8 modules (SM, FM, CP) are permitted per rack.
• The number of modules (SM, FM, CP) is limited by the permitted current consumption on
the S7-300 backplane bus. The accumulated power consumption may not exceed 1.2 A
per row.
Note
For information on the power consumption of the various modules, refer to the
Module
Specifications Reference Manual.
Rules: Interference-proof interfacing
Special shielding and grounding measures are not required if you interconnect the CU and
EM using suitable interface modules (Send IM and Receive IM).
However, you must ensure
• a low impedance interconnection of all racks,
• that the racks of a grounded assembly are grounded in a star pattern,
• that the contact springs on the racks are clean and not bent, thus ensuring that
interference currents are properly discharged to ground.
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