How can you design a Profibus DP network for high-speed data exchange?

1 Network topology

The network topology defines how the masters and slaves are connected to each other. There are three main types of topology for Profibus DP: linear, star, and tree. Linear topology is the simplest and most common one, where the devices are connected in a chain. Star topology is where the devices are connected to a central hub or switch. Tree topology is where the devices are connected to multiple hubs or switches, forming branches. The choice of topology depends on the number and location of the devices, the availability of power supply, and the redundancy requirements.

3 Termination resistors

The termination resistors are used to prevent signal reflections and distortions on the network, which can cause data errors and communication failures. They are placed at both ends of each segment, between the signal wires and the shield. The value of the termination resistors depends on the characteristic impedance of the cable, which is typically 150 ohms for Profibus DP. The termination resistors must be activated only at the end devices, and deactivated at the intermediate devices.

4 Data rate

The data rate defines how fast the data is transmitted on the network, measured in bits per second (bps). The higher the data rate, the faster the data exchange, but also the higher the risk of signal degradation and interference. Profibus DP supports data rates from 9.6 kbps to 12 Mbps, depending on the cable type and the segment length. The choice of data rate depends on the application requirements, such as the cycle time, the data volume, and the response time.

5 Segment length

The segment length defines how long each part of the network is, measured in meters. The longer the segment length, the more devices can be connected, but also the lower the data rate and the higher the attenuation. Profibus DP has different segment length limits for different data rates and cable types, as specified in the standard. The segment length must not exceed these limits, otherwise the network performance and reliability will be compromised.

6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?