Diagnostic mechanisms

The diagnostic concept of PROFINET is primarily based on the integrated diagnostic functions in the PROFINET protocol. As the devices support TCP/IP communication, they are also able to use SNMP (Simple Network Management Protocol) or web server technologies for diagnostics.

PROFINET diagnostics

PROFINET diagnostics  

Diagnostic mechanisms in PROFINET

In the context of PROFINET diagnostics, devices use cyclic I/O transfer to indicate an error. Parallel to this, an alarm is generated via acyclic communication and indicated to the controller.

Alarms can be divided into two groups:

  • Error states are sent as diagnostic alarms with corresponding parameters. The parameters can contain either PROFINET-specific error codes, device-specific error codes or device-specific error arrays.
  • Wear indicators or similar information associated with accelerated diagnostics can be reported via two priority levels for maintenance requirements.

The corresponding text information regarding the cause of an error code is available in the device-specific GSD file. This means that diagnostic tools can display all error messages as user-friendly text. The more detailed the error message provided by the device, the more precise the diagnostics displayed in the controller or engineering system.

Topology detection

Topology detection with PROFINET  

Even extensive networks can be displayed clearly

To pinpoint the exact location of diagnostic messages in a network with flexible cable connections, PROFINET uses the Link Layer Discovery Protocol (LLDP) standardized by the IEEE. While the connection is being established, the devices exchange device names and port numbers with neighboring components via LLDP.

Device names must be unique as they are used for addressing purposes during device data exchange. The information regarding neighboring components retained in the devices can be read using SNMP or the PROFINET protocol.

If all of the devices in the network support LLDP, a precise topology image can be displayed in the diagnostic tool. This enables error messages to be displayed directly at the device or port.

SNMP and web-based diagnostics

SNMP and web-based diagnostics  

Diagnostics via web server or SNMP manager

In addition to typical PROFINET mechanisms, this fieldbus system offers other useful functions: the Simple Network Management Protocol (SNMP) is an established global Ethernet standard for network management.

The SNMP agent, which can send error messages such as SNMP traps to the SNMP manager or a trap receiver, runs on the PROFINET devices. The trap receiver displays the messages or uses SNMP to retrieve additional device information.

A web server is another possible diagnostic tool. Many of today's devices feature integrated web servers. Web servers are used to call diagnostic pages directly on devices via HTTP with a standard browser on a PC platform. They provide every manufacturer with an optimum display tool for their diagnostic information without having to install a diagnostic tool on the PC platform.


C6 The Exchange
Calmount Park
Dublin 12
D12 XE18