Installing the S7-400
2-5
Automation System S7-400 Hardware and Installation
A5E00850741-01
Rules for Connection
When you c onnect a central rack to expansion racks, you must observe the
following rules:
• You can connect up to 21 ERs of the S7-400 to one CR.
• The ERs are assigned numbers to identify them. The rack number must be set
on the c oding switch of the receive IM. Any rack number between 1 and 21 may
be assigned. Numbers must not be duplicated.
• You may insert up to six send IMs in one CR. However, only two send IMs with
5 V transfer are allowed in one CR.
• Each chain connected to the interface of a send IM can comprise up to four ERs
(without 5 V transfer) or one ER (with 5 V transfer).
• The exchange of data via the communication bus is limited to 7 racks, meaning
the CR and ER numbers 1 to 6.
• The maximum (total) c able lengths specified for the type of connection must not
be exceeded.
Type of Connection Maximum (Total) Cable Length
Local connection with 5 V transfer via
IM 460-1 and IM 461-1
1.5 m
Local connection without 5 V transfer via
IM 460-0 and IM 461-0
5m
Remote connection via IM 460-3 and
IM 461-3
102.25 m
Remote connection via IM 460-4 and
IM 461-4
605 m
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