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RSLinx/ControlLogix Data Collection

ObjectivesObjectives

• Discuss Common ControlLogix Data Collection Problems

• Offer Solutions to Resolve These Issues

Common Data Collection IssuesCommon Data Collection Issues

• Data updates are slow• Batch/Recipe downloads fail – Not all of the

data gets to the CLX• Performance degrades when adding more HMI

stations• Switching between different HMI screens takes

too long• Items stop getting updates• Items stop getting updates temporarily• Other Issues?

ControlLogix BandwidthControlLogix Bandwidth• Relevant Issue:

– Data updates are slow

• Allocate enough time for communications • ControlLogix processing power needed for

communications varies– System overhead time slice (continuous tasks)– Time between periodic tasks are scheduled (periodic

tasks)– Number of Tags– Arrays, vs. UDT optimization, vs. scattered

optimization– Motion and IO use communications bandwidth

Tasks and CommunicationsTasks and Communications• Continuous Tasks

– Communication time is interleaved with running PLC code– Communication time allocated is proportional to time slice– Continuous task time will increase as time slice increases if

more communications bandwidth is needed– Default task type

• Periodic Tasks– Communications are halted while running PLC code– Task execution time is not effected by communications– The less frequently task is scheduled, more time for

communications– Tightly scheduled periodic tasks will limit communications

Tasks and CommunicationsTasks and Communications

• Using a Continuous Task and a Periodic Task– You are not required to have a periodic task– Reduces communications bandwidth– Tightly scheduled periodic tasks will limit

communications

• Multiple Periodic Tasks– Adds complexity to scheduling them and allocating

communications bandwidth– Reduces communications bandwidth

RecommendationsRecommendations

• Use One Continuous Task or One Periodic Task

• Consider Consolidating Time Critical Control from Data Collection into Separate ControlLogix Processors

Periodic Task SchedulingPeriodic Task Scheduling

• Periodic Task of 63 (ms)

• 5000 DINT Tags on Scan

Periodic Task Rate

Tags Per Second

64 260

70 1300

100 4840

200 8890

300 10250

400 10950

500 11350

Time SliceTime Slice

• Continuous Task

• 5000 Tags on Scan in a 5555 (No Arrays or UDTs)

Time Slice Max Scan Time

Tags per Second

10% 139 1270

20% 158 2680

30% 183 4070

40% 218 5340

50% 266 6620

60% 339 7940

70% 465 9190

80% 695 10360

90% 1472 11530

Tag Organization and CommsTag Organization and Comms

• Relevant Issue– Data Updates are slow

• Use arrays when possible– Less ControlLogix CPU needed – Less ControlLogix memory used

• Use UDTs and Design Them with HMI in Mind– Performance similar to arrays – The more UDT elements consumed by data

collection the better– RSLinx UDT optimization must be enabled– RSLinx must be able to optimize the UDT (480

bytes)

Memory ConsumptionMemory Consumption

• 5000 Tags on Scan in a 5555

Tag Type Tags Per second

ControlLogix Optimized Packets

CLX Memory

Consumption (Bytes)

Isolated Integers

975 41 208,828

Integers in UDTs

6600 23 18,372

Array of Integers

7240 21 17,860

Optimize Batch/Recipe DownloadsOptimize Batch/Recipe Downloads

• Relevant Issue – Batch/Recipe downloads fail – Not all of the data

gets to the CLX

• Use Write Optimization– ControlLogix Processor firmware 10.x or higher– RSLinx 2.30.02 or higher– RSLinx topic with optimize poke packets enabled

• UDT Optimization– ControlLogix batch applications often use UDTs– As recipes run they often access various elements in

the same UDTs

Optimize Batch/Recipe DownloadsOptimize Batch/Recipe Downloads

Scalability – Getting Data into Multiple StationsScalability – Getting Data into Multiple Stations

• Relevant Issue– Performance degrades when adding more

HMI stations

• Use RSLinx Gateway (Remote OPC)– Optimizes network traffic and ControlLogix

CPU– ControlLogix CPU and connections

consumed for each RSLinx

Performance Degrades Without RSLinx GatewayPerformance Degrades Without RSLinx Gateway

• 5000 Tags on Scan in a 5555 (No Arrays or UDTs)• 50% Time Slice• 1 GHz Pentium III machines

Number of RSLinx stations collecting Data

Time between updates

Tags per Second

1 .74 6710

2 1.56 3355

3 2.1 2220

4 2.95 1660

5 3.7 1340

RSLinx Gateway for ScalabilityRSLinx Gateway for Scalability

• 5000 Tags on Scan in a 5555 (No Arrays or UDTs)• 50% Time Slice• 1 GHz Pentium III machines

Number of Remote OPC Stations Collecting Data from an RSLinx Gateway

Time between updates

Tags per

Second

RSLinx Gateway Virtual Memory (M)

CPU utilization of RSLinx Gateway

1 .75 6710 30.01 36%

2 .75 6710 33.11 47%

3 .75 6710 33.72 47%

4 .75 6710 34.3 55%

5 .75 6710 36.93 71%

Operating/Maintaining SystemsOperating/Maintaining Systems

• Relevant Issue– Data stops updating

• Data Collection Must Be Stopped and Restarted– Deleting tags in a ControlLogix Processor – Changing data type of a tag in a ControlLogix Processor– Changing array length of a tag in a ControlLogix Processor– Changing an alias tag in a ControlLogix Processor– Changing a UDT structure in a ControlLogix Processor

• Data Collection Can Continue Uninterrupted – Adding tags to a ControlLogix processor– Adding tags to data collection applications

Operating/Maintaining SystemsOperating/Maintaining Systems

• Relevant Issue– Data stops updating

• When ControlLogix Processor Tags Need To Be Changed or Deleted– Schedule a time for the ControlLogix downloads and

employ a procedure to make updates – Don’t have to shut down HMIs– RSView has a NodeDisable command for example– Data collection can stop and start after the

ControlLogix download

RedundancyRedundancy• ControlLogix Hardware (processor, modules, power

supply)– Two redundant racks synchronized by a 1757-SRM Module– Both redundant racks seen as one rack by RSLinx

• Network, ControlLogix Hardware - RSLinx Alias Topics– Use switch on command only– Monitor a heartbeat on primary and backup(s). – Switch topics if heartbeat stops updating.

• PC, Software, NIC – – RSLinx server redundancy– Multiple RSLinx Gateways

More InformationMore Information

• Application Guide - CLXPerf– http://www.software.rockwell.com/download/

comms/rslinx/clx_perf.zip

• Troubleshooting Guide– http://www.software.rockwell.com/download/

comms/rslinx/controllogix%20data%20collection%20troubleshooting%20guide.doc