Siemens CPU 313C Hardware And Installation Manual page 35

5XOHV $UUDQJLQJ PRGXOHV RQ PXOWLSOH UDFNV
Please note the following points if you wish to arrange your modules on multiple
racks:
• The interface module always uses slot 3 (slot 1: power supply; 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 load
on the S7-300 backplane bus. The total power consumption must not exceed
1.2 A per row.
1RWH
The power consumption of the individual modules is given in the 0RGXOH 'DWD
5HIHUHQFH 0DQXDO
5XOHV ,QWHUIHUHQFHSURRI LQVWDOODWLRQ RI WKH FRQQHFWLRQ
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 that
• all racks are interconnected with low impedance,
• the racks of a grounded assembly are grounded in a star pattern,
• the contact springs on the racks are clean and not bent, thus ensuring that
interference currents are dissipated.
S7-300 Automation System, Hardware and Installation: CPU 31xC and CPU 31x
A5E00105492-03
&RQILJXULQJ
5-9