4 Cabling the AC 800F
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4.3.2.3 Connection via RS485 interface
Up to 32 nodes can be connected in parallel to the bus-compatible RS485 interface.
• Connect the serial fieldbus module FI 820F with the terminal block TB 870F using
cable TK 821F. Only hand-tighten the screws.
• Put on the TK 821F cable shield. Connect it to the AC 800F contact ledge using a
clip TV 83xF.
• Connect the appropriate interface channel 0 and channel 1 to the terminal block
TB 870F, using the terminals specified below. Use a shielded twisted-pair cable,
e. g. 2 x 2 x 0.25 mm² or 1 x 2 x 0.25 mm² if you do not want to connect to GND.
• Observe the max. cable length of 1200 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.
Channel 0 on terminal block TB 870F
RxTx+ Combined transmit/receive data (input/output) Pin 7
RxTx- Combined transmit/receive data (input/output) Pin 8
GND Ground Pin 5
Channel 1 on terminal block TB 870F
RxTx+ Combined transmit/receive data (input/output) Pin 20
RxTx- Combined transmit/receive data (input/output) Pin 21
GND Ground Pin 18
With RS485 transmission one wire pair provides for time-multiplexed, differential
transfer of the transmit and receive data. This means that the FI 820F can either
transmit or receive data at the same time (half-duplex operation). The GND
connections are not needed when cabling the module in the field, they are only used
for measuring and testing in the commissioning phase. Please note that the offset
voltage bet ween GND and the signal lines is less than ± 7 V. Observe the max.
permissible cable length of 1200 m.
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