GE PACSystems RXi User Manual

Chapter 10. PROFINET IO-Controller OperationGFK-2816F August 2015 20510.1.3 Types of PROFINET CommunicationsThe PNC uses two types of PROFINET communication transfers: real-time and non-real-time. The illustration below shows real-time communications as solid lines and non-real-timecommunications as dashed lines.RXi Controllerwith PNCNon-real-time data:parameters, configuration, etcReal-time data:Inputs, Outputs,AlarmsPROFINETIO-DevicePROFINETIO-DeviceRXiController■ Real-Time (RT) communication: PROFINET real-time communication is used for time-sensitive data. A PROFINET IO-Controller and PROFINET IO-Device use two types ofreal-time communications to exchange data: cyclic communication and acycliccommunication:- Real-time Cyclic communication is used to periodically transfer the application’s inputand output data. Cyclic communication occurs each PROFINET IO production cycle.- Real-time Acyclic communication is used to transfer non-periodic data such asalarms. Acyclic communication occurs only when needed.■ Non-Real-Time (NRT) communication: PROFINET non-real-time communication isused for less time-sensitive data such as configuration, parameterization, diagnostics,and identification data.10.1.4 External Switch VLAN Priority SettingsThe PROFINET-IO specification indicates the VLAN priorities for each type of Ethernet trafficthat originates from a PROFINET node. VLAN priorities range from 0 to 7, with 7 being thehighest.The switch on the PNC supports just four traffic classes, giving four levels of preference.Incoming traffic without a VLAN priority is assigned to the lowest priority traffic class. Thetable below lists the VLAN priorities, and their corresponding priorities in the PNC:VLANPriority PNC Priority Ethernet Traffic Description7 Highest priority MRP Media Redundancy6 Second-highestpriorityRT_CLASS_1 Cyclic PROFINET IOHigh Priority RTA_CLASS_1 High-Priority PROFINET Alarms5 Third-highestpriorityLow Priority RTA_CLASS_1 Low-Priority PROFINET Alarms4, 3, 2, 1 Lowest priority (reserved) (reserved)0 IPDCPDevice Discovery andConfigurationIf a system includes external switches, these switches must be configured to match the VLANPriority groupings listed above for the PNC.