PROFNET IO connection life-cycle

The PROFINET IO connection life-cycle describes the connection between a PROFINET IO Controller and IO Device. The connection allows the cyclic exchange of process IO data, and the acyclic handling of alarms. The PROFINET IO connection life-cycle consists of address resolution, connection establishment, parameterization, process IO data exchange / alarm handling, and termination.[1]

Address resolution

A PROFINET IO device is identified on the PROFINET network by its station name.[note 1] Connection establishment, parameterization and alarm handling are implemented with User Datagram Protocol (UDP), which requires that the device also be assigned an IP address. After identifying the device by its station name, the IO controller assigns the pre-configured IP address to the device.[1]

Connection establishment

Connection establishment starts with the IO Controller sending a connect request to the IO Device. The connect request establishes an Application Relationship (AR) containing a number of Communication Relationships (CRs) between the IO Controller and IO Device.[2] The connect request defines some CRs within the AR. The following CRs are supported:

  1. IO data CR’s support the point-to-point exchange of cyclic input and output process data between the IO Controller and IO Device.
  2. A record data CR supports the exchange of log data.
  3. An alarm CR supports the handling of alarms.
  4. A multicast CR allows cyclic process data to be published by one node for consumption by any number of consumers.[1]

In addition to the AR and CRs, the connect request specifies the modular configuration of the IODevice, the layout of the process IO data frames, the cyclic rate of IO data exchange and the watchdog factor.

Acknowledgement of the connect request by the IO Device allows parameterization to follow. From this point forward, both the IO Device and IO Controller start exchanging cyclic process I/O data frames. The process I/O data frames don't contain valid data at this point, but they start serving as keep-alive to keep the watchdog from expiring.

Parameterization

The IO Controller writes parameterization data to each IO Device sub-module in accordance with the General Station Description Mark-up Language (GSDML) file. Once all sub-modules have been configured, the IO Controller signals that parameterization has ended. The IO Device responds by signalling application readiness, which allows process IO data exchange and alarm handling to ensue.[1][2]

Process IO data exchange / alarm handling

The IO Device followed by the IO Controller start to cyclically refresh valid process I/O data. The IO Controller processes the inputs and controls the outputs of the IO Device.[2] Alarm notifications are exchanged acyclically between the IO Controller and IO Device as events and faults occur during this phase in the PROFINET IO connection life-cycle.[1]

Termination

The connection between the IO Device and IO Controller terminates when the watchdog expires.[2] Watchdog expiry is the result of a failure to refresh cyclic process I/O data by the IO Controller or the IO Device.[1] Unless the connection was intentionally terminated at the IO Controller, the IO Controller will try to restart the PROFINET IO connection life-cycle.

Notes

  1. ↑ The station name is a user-configurable alpha-numeric description of up to 240 characters

See also

  1. PROFINET

References

  1. 1 2 3 4 5 6 PROFINET System Description, Version April 2009, PROFIBUS Nutzerorganisation e.V., 2009
  2. 1 2 3 4 Industrial communication with PROFINET, Manfred Popp, Order no.: 4.182, PROFIBUS Nutzerorganisation e.V. (PNO)

External links

  1. PROFIBUS & PROFINET International (PI)
  2. All Things PROFINET
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