ABB AC 800F

4 Cabling the AC 800F
4-58
Pin Signal Description
1 shield shield
2 n. c. not used
3 RxD+/TxD+ receive / transmit data - PLUS
4 RTS repeater control signal (direction control)
5 GND data transmission potential (ground to 5 V)
6 VP 5 V supply voltage of terminating resistors
7 n. c. not used
8 RxD-/TxD- receive / transmit data - MINUS
9 n. c. not used
Transmission technology
Data transmission in accordance with the standard from the fieldbus module to the
fieldbus devices is normally realized via:
• RS485 link
• fiber optic cables (FO cables) with the appropriate converters from another
supplier, for RS485 ➩ FO cable and FO cable ➩ RS485 transition.
4.3.1.1 Connecting the Profibus via RS485
A shielded TP (twisted pair) copper cable is the hardware required for RS485
transmission. It connects all devices to the bus structure (line). The bus structure
allows for non-reactive coupling and decoupling of stations or stepwise
commissioning of a system. Later extensions have no impact on stations that are
already working on the bus.
Up to 32 nodes (master and slaves) can be grouped in a single segment. When using
more than 32 nodes, several segment linked to each other through repeaters (power
amplifiers) are needed. Note that the repeater has to be considered as another bus
node, since the integrated bus drivers are an additional load on the bus. It is
recommended to use not more than three series-connected repeaters on a line.
The Profibus connector links the individual data lines with each other and ensures that
the failure of a node does not impair the other nodes. Nevertheless, a distinction is
made between the incoming and outgoing data line. Connectors designed for trans-
mission rates of more than 1.5 Mbauds are provided with series impedances in the
incoming line.