4 Cabling the AC 800F
4-83
4.3.3 Redundant cabling of two serial fieldbus modules
The following section describes the redundant connection of the serial fieldbus
module for RS232, RS422 and RS485 using examples.
Only the external termination with external power supply is described for the
differential cabling methods (RS422, RS485), as only this is relevant for redundancy.
Do not use an internal termination or an external termination with internal
power supply. Otherwise, trouble-free operation in case of errors or after
module replacement is not ensured, and redundant cabling will have
not effect.
4.3.3.1 Redundant connection via RS232 interface
Note that only the primary unit is allowed to actively transmit data. The secondary unit
must set its interface to high resistance. Communication between the primary and the
secondary unit is not possible via this interface, since both their transmit signals and
their receive signals are linked to each other.
• Link two redundant fieldbus modules with the terminal block TB 870F using cable
TK 821F. Only hand-tighten the screws.
• Put on the TK 821F cable shields. Connect them to the two AC 800F contact
ledges using clips TV 83xF.
• Connect the appropriate interface, channel 0 and channel 1, on the terminal
blocks using the specified terminals and establish a connection to the RS232
device. Use a shielded cable e.g. 5 x 0.14 mm
2
or 5 x 0.25 mm
2
• Observe the max. cable length of 15 m.
• Apply the shield to terminal P of the terminal block.
If the shield is not put on properly, neither RFI suppression nor
EMI/RFI shielding of the system can be guaranteed.
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