Omron CJ1W-CRM21, Operation Manual

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A-4 PROFINET Communication Services
The IO Controller establishes a connection to its IO Devices based on the
configuration which has been given by the user. The Application Relation (AR)
includes all data needed to achieve this data exchange. A single AR can
include multiple Communication Relations (CRs). For implementation of
different communication profiles, such as PROFIdrive, the PROFINET IO
contains special addressing elements. These elements are called Application
Process Identifier (APIs).
The following CRs are possible for each API.
• IOCR, consisting of input, output or multicast
• Record data CR for exchange of acyclic data
• Alarm-CR for communicating alarms and other events
The data exchange between the IO Device and the IO Controller occurs in a
poll cycle as configured by the IO Controller. The user is capable to set this
update cycle in the IO Controller configuration for each of the IO Devices. This
results in mutual monitoring of functional operability (watchdog function). All
cyclic data is provided with a status that encodes the validity of the data.