According to the IEC 61158/EN 50170 standard, Profibus DP (decentralised periphery)

is typically used to connect decentralised peripheral devices with fast response times.

The standard specifies node distances of up to 300 metres with bit rates

ranging from 9.6 kbps to 12 Mbps, using standard cables and maintaining maximum operating speed.

Transmission method

The transmission method for Profibus DP is the RS485 interface

(according to the EIA standard) using shielded twisted-pair cables.

The simple RS485 twisted-pair transmission method is ideally

suited for linear/tree networks with high transmission speeds.

The Profibus must always be terminated with two terminals.

As shown in the figure below, either terminal must consist of three resistors;

The terminals must be fed with a voltage of 0 to 5 volts DC,

otherwise their resistance is not equal to the characteristic impedance of the cable.

With this structure, the voltage on the bus is fixed when there are no active devices.