Profibus network characteristics

The Profibus network extension by means of signal segmentation and regeneration

is limited to a maximum of 32 nodes/partners (master/slave) per segment;

On the other hand, the entire network can have up to 126 nodes/partners.

If you need to increase the length of the bus or use more than 32 stations, you must use repeaters.

Any repeater is a ‘load’ on the bus. Each new segment introduced 

must be terminated at both ends of the segment, the maximum length

of which depends on the baud rate; however, standard procedure is to connect up to 30 loads per

segment.

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.