ABB AC500 PLC - Page 1292

Pin Signal Description
8 RxD/TxD-N Reception / transmission line,
negative
9 CNTR-N Control signal for repeater,
negative (optional)
Parameter Value
Type Twisted pair (shielded)
Characteristic impedance 135 Ω...165 Ω
Cable capacity < 30 pF/m
Conductor diameter of the cores ≥ 0.64 mm
Conductor cross section of the cores ≥ 0.34 mm²
Cable resistance per core ≤ 55 Ω/km
Loop resistance (resistance of two cores) ≤ 110 Ω/km
The maximum possible cable length of a PROFIBUS subnet within a segment depends on the
baud rate (transmission rate).
Baud Rate Maximum Cable Length
9.6 / 19.2 / 93.75 kBaud 1200 m
187.5 kBaud 1000 m
500 kBaud 400 m
1.5 MBaud 200 m
3 MBaud to 12 MBaud 100 m
Branch lines are generally permissible for baud rates of up to 1500 kbit/s. But in fact they should
be avoided for transmission rates higher than 500 kbit/s.
The line ends (of the bus segments) have to be terminated using bus terminating resistors
according to the drawing below. The bus terminating resistors are usually placed inside the bus
connector.
390 Ohms
220 Ohms
390 Ohms
VP (+5 V)
GND (0 V)
RxD/TxD-P
RxD/TxD-N
Data Line B
Data Line A
6
3
8
5
One bus segment can have up to 32 subscribers. Using repeaters a system can be expanded to
up to 126 subscribers. Repeaters are also required for longer transfer lines. Please note that a
repeater's load to the bus segment is the same as the load of a normal bus subscriber. The sum
of normal bus subscribers and repeaters in one bus segment must not exceed 32.
Bus Cable
Cable Lengths
Bus Terminating
Resistors
Repeaters
System Assembly, Construction and Connection
AC500 (Standard) > Connection and Wiring
2019/04/173ADR010121, 13, en_US1292