PROFINET RT vs IRT - Siemens

1 Unrestricted Siemens Siemens 2020 PROFINET RT vs IRTU nrestricted Siemens 2020 Communication BasicsEthernet + PROFINET = Industrial EthernetPage 2 PROFINET is complimentary to Ethernet PROFINET is Industrial Ethernet PROFINET devices include IO-controllers and IO-Devices PROFINET is Fast Ethernet ie100 Mbit/s Full Duplex PROFINET devices, connectors and cable are suited to industrial applicationsIO-ControllerIO-DevicesUnres tricted Siemens 2020 Communication BasicsTransmission methodsPage 3 PROFINET follows a Consumer-Provider Model Cyclic, deterministic data transfer for time-critical applications Prioritization of time-critical data Acyclicdata transmission for configuration, monitoring and diagnostics/alarmingAcyclic Data: Parameterization, Diagnostics, Monitoring/ControllingCyclic Data:Process DataAcyclic Data.

2 Configuration, AlarmsIO-ControllerIO-DeviceIO-Superviso rUnrestricted Siemens 2020 Communication BasicsProfinet communication channelsPage 4 None Real Time (NRT) <100ms cycle Acyclic Uses TCP/IP Left laneReal Time (RT) <10ms cycle Cyclic Skips the TCP/IP layers Over taking laneIsochronous Real Time (IRT) <1ms cycle Cyclic Reserved Bus laneNRTNRTIRTRTRTRTNRTNRTNRTIRTIRTU nrestricted Siemens 2020 Open ControllerS7-1200 Page 5 FunctionS7-1500IO-ControllerRTIRTC ontrollerS7-300 / S7-400 Communication BasicsController selectionRT ~80% applications require RT only In this case any controller is suitableIRT The remaining applications will require high speed capabilities Synchronised Motion Precision Measuring Precision IO Ethernet switches can be used but selection guidelines must be followed ieIRT = Conformance Class CNRTU nrestricted Siemens 2020

3 ApplicationPresentationSessionTransport (TCP)Network (IP)Data LinkPhysicalCommunication BasicsOSI7layermodelPage 62345671 PROFINET RTIEEE 802 PROFINET RTPROFINET NRT Each layer adds processing time NRT is used for configuration, web server, diagnostics and other none real time tasks RT is typically used for standard cyclic data acquisition IRT is used for high speed data transferPROFINET IRTM odified IRTPROFINET NRTC yclic Data:Process DataAcyclic Data: Configuration, Diagnostic/AlarmsUnrestricted Siemens 2020 Communication BasicsOSI7layermodel closer lookPage 7 The OSI layer model for structured communicationPhysicalData linkNetworkTransportSessionPresentationA pplication1234567 EthernetIPTCP, UDPS ervices100 Base TX/FXLayerHTTP, SNMP dataEthernetTrailerIPHeaderTCPH eaderuser dataTCPH eaderuser dataEthernetHeaderPNHeaderPNApplication dataEthernetTrailerWeb pages, email, live pictures, Siemens 2020 PROFINET RTNo synchronization of cyclesPage 8T1T2T3T4T7T6T5 Various uncoordinated cycles T1.

4 Sampling of input T2: backplane bus ET 200 T3: ProfinetI/O T4: CPU cycle (OB1) T5: ProfinetI/O T6: backplane bus ET 200 T7: setting outputTime precision of output signal(OB1-output)2 x sum of all cycles from CPU to output (T4 -T7)ControllerDeviceDeviceReaction time (input-output) Best case: sum of all individual cycles Worst case: 2 x (sum of all individual cycles)RT Real Time: Real-time communication between controller and device Each device has its own update time Processing in the standard user program ( OB1)InputOutputUnrestricted Siemens 2020T1T2T3T4T7T6T5TI: Read in ALL inputs of ALL devicesat a fixed predefined timeProfinet IRTI sochronous mode for fast reaction timePage 9T1T2T3T8T7T6T5 ControllerDeviceDeviceTOQOBIQOBIQOBIS ystem clockTIOB: processing in the CPUTO: Writes ALL outputs of all devicesat a fixed predefined timeIRT IsochronousReal Time.

5 All cyclesare synchronizedwith each other Special hardware is needed ieHF modules IRT packets are transmitted in a reserved bandwidth Isochronous mode: Synchronized processing in the user program using "synchronous cycle" OB6x (T8)InputOutputUnrestricted Siemens 2020 Cycle timeTime based IOOversamplingTypical 500 s cycleCPU1518 : 125 sBy optimized packing of data the transmission time gets reduced: Less time on LAN More time of the cycle for Sync-OB More time for Non-IRT on LANP eripheral module separates PN cycle into smaller sampling cycle. All samples are sent to the and falling edge of signal are transmitted with timestamp high precision signal capturingOutputs triggered with timestamp high precision reactionI/O update time1ms12345678910111213141516 Value capturingSending 16 valuesSystem update timeEt1t2 TIO Timet := t2-t1;s := v * t.

6 Synchronous OBProfinet IRTA dditional capabilitiesPage 10 Unrestricted Siemens 2020 PROFINET RT/IRTF unctional OverviewPage 11 Real-time communication Update time >=250 s Applications: manufacturing engineering building automation automation equipmentRT Real-time communication with reserved bandwidth and synchronized cycles Update time >=125 s Special hardware Requirement for isochronous mode Applications: Motion control Precise reactions Real-time communication with synchronized OB61 Synchronization of the user program to all other synchronized cycles Requirement for further functions Oversampling and time-based IO Applications.

7 Motion control Precise reactions measuringtechnologyIRTI sochronousUnrestricted Siemens 2020 PROFINET IRTKey requirementsPage 12 Define Topology in TIA Topology view oEnsures optimised data transferoAllows scheduled transfers Configure interface real time settings and set synchronization role Ensure correct settings for the sync domainoOptional High performanceoOptional Fast forwardingUnrestricted Siemens 2020 PROFINET IRTKey requirementsPage 13 Insert Synchronous OB6x or Motion OBEnable Isochronous mode on each IO Device Will ensure IO is sync d with Motion or OB6xUnrestricted Siemens 2020 PROFINET IRTIRT in reality(oscilloscope)Page 14 IRT on the oscilloscope vs.

8 TIA Portal TIA / Step7 calculates timing beforehand Reaction time predefined Live result as expectedData processingData InData OutIRT RT/NRTNRTtController ApplicationT_DCn (CACF = 1)Controller ApplicationT_DCn+1 (CACF = 1)Controller ApplicationT_DCn-1 (CACF = 1)T0 TITime of acquisitionTime of output (response to the process)Minimum response timeMaximum response timeChange of the input signalTime of acquisition referring to the IRT-cycleTime of output referring to the IRT-cycle= TI + T_DC + T0= TI + 2xT_DC + T0 Time IO Output ValidTIData transmission on the busPeripheral deviceData processingData processingControl unitInputOutputUnrestricted Siemens 2020 PROFINET IRTT imeslicemodel Page 15 Partitioning of the bus cycle Separate time slices (time domains) for IRT and rest (RT, TCP/UDP.)

9 High precision cycle synchronization Based on optimized switch ASIC special hardware neededCycle 1 Cycle 2= time domainCycle nIRT-channelStandard channel Isochronous communicationRT/ StandardcommunicationIRT-channelStandard channel 1 ms position control cycleIRT-dataSynchro-nizationRT-data / TCP/IP-dataUnrestricted Siemens 2020 PROFINET IRTT imeslice model in detailPage 16 Cycle 1 Cycle 2 IRT-channelStandard channel IRT-channelStandard channel Send clock 500 s 1msPN IORT/IRTNRT0%50%100%Send clock > 1msPN IORT/IRTNRT0%500 sfix1,125 4msmax 50% PN0-500 s~ 50% - 12,5% PN0-500 sSend clock 250 sPN IORT/IRTNRT0%100 sfix250 s40% PN0-100 sOverviewin TIA Portal: Reserved bandwidth can be set in TIA Portal Used bandwidth is displayed separately for IRT and RTFixed bandwidth for IRT in theory.

10 1212 Unrestricted Siemens 2020 PROFINET IRTFast forwardingPage 17 To forward frames, a device needs to see the frame ID This typically takes 1440ns Using performance mode, this is improved to 320ns Frame ID leads the PROFINET frameUnrestricted Siemens 2020 PROFINET IRTD ynamic Frame PackingPage 18 Each DFP frame includes a specific device data along with other devices on the line Each device takes its data and forwards on This leads to an overall improvement in network bandwidthUnrestricted Siemens 2020 PROFINET IRTF ragmentationPage 19 A complete standard Ethernet TCP/IP frame takes 125uS so cycle time cannot be reduced Performance mode allows fragmentation of these frames into sub frames Cycles times <250us are achievable