GE 90-70 manual Incompatible Configurations, Resynchronization of a Redundant CPU

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Incompatible Configurations

When two units have incompatible configurations stored (for example, both units configured for PRIMARY or differing blocks for data transfer), then only one of the units can go to RUN mode. If the other unit attempts to go to RUN mode or both units attempt to go to RUN mode at the same time, a FATAL incompatible configuration fault will be logged.

If one unit is configured for CPU Redundancy and the other has no configuration, then both units may go to RUN mode at the same time but they will not be synchronized and only the unit that has been configured will drive outputs.

Resynchronization of a Redundant CPU

When a CPU attempts to get back in synchronization with the currently active CPU, resynchronization occurs. Resynchronization occurs any time a CPU transitions from STOP to RUN mode. The process starts by determining which role each CPU is to play, based on configured control strategy and PRIMARY/SECONDARY configuration as shown in the table below.

Control Strategy

Behavior during Resynchronization

GHS

GDB

The Primary Unit (with Serial Bus Address 31) is always preferred. A switch occurs from the Secondary Unit each time the Primary Unit resynchronizes. Until the resynchronization is complete, the Primary Unit acts as backup.

The Primary Unit switches to active just prior to logic execution. Outputs will be driven that sweep by the Primary Unit.

The active CPU remains active after resynchronization without regard to whether it is in the Primary or Secondary unit. The transitioning unit becomes the backup.

If both systems are transitioning at the same time, the Primary Unit becomes the active CPU and the Secondary Unit becomes the backup.

During resynchronization, the CPUs exchange information about roles and configuration. If the transitioning CPU detects that the role or configuration is not in agreement, that CPU is not permitted to go to RUN mode. If both CPUs are transitioning, neither CPU is permitted to go to RUN mode. The following items must be in agreement:

1.One CPU must be configured as Primary, the other as Secondary.

2.Both CPUs must be configured for the same control strategy (GHS or GDB).

3.Both CPUs must have the same Shared I/O redundancy points configured.

4.If point faults are enabled on one CPU, they must also be enabled on the other if %I, %Q, %AI, or %AQ data is transferred.

At this point, the active unit is the one that has been in control and the backup unit is the one that is resynchronizing. The transfer of all configured control data from the active unit to the backup occurs unless both units are transitioning at the same time (transfer always goes from the running unit to the resynching unit. In addition to the configured control data, the FST_SCN and FST_EXE %S references as well as internal timer information for each common (that is, present in both CPUs) sub-block are transferred from active to backup. Only the internal timers and

GFK-1527A

Chapter 4 Normal Operation

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Contents GE Fanuc Automation GFL-002 Content of This Manual PrefaceRelated Publications Preface Contents Contents Chapter Fault Detection Appendix a Cabling Information Introduction Definition of TermsEnhanced Hot Standby CPU Redundancy Using the Redundancy CPU for Non-Redundant Operation Compatibility with CPU780Features not Available with Redundancy CPUs Redundancy CPUs as Compared to Other Series 90-70 CPUsDifferences in Operation for Redundancy CPUs Redundant Racks Enhanced Redundancy CPU ModuleRedundancy Communications Module Systems for Enhanced Hot Standby CPU RedundancyGenius I/O Local I/OCable Connections Enhanced Hot Standby CPU Redundancy System with Local I/O Local I/0 Can beControl Strategies GHS Control StrategyGDB Control Strategy Basic Enhanced Hot Standby Operation Output Control with GHSOutput Control with GDB Basic CPU Redundancy Setups Single Bus with Preferred Master GHS Control StrategySingle Bus with Floating Master GDB Control Strategy Critical Data + Redundant Outputs TransferredDual Bus with Floating Master GDB Control Strategy Paired GBC = INT/EXT Internal ExternalOnline Programming On-Line RepairDuplex CPU Redundancy For Installation Instructions System ComponentsSystem Racks Features Redundancy CPUWatchdog Timer CPU ArchitectureExpansion Memory Board Battery Connectors CPU FeaturesMemory Protect Keyswitch CPU LEDsCPU Mode Switch PortRedundancy Communications Module Unit Select PushbuttonConnector RCM Status LedsConnectors Bus Transmitter ModuleBus Transmitter Module Status LEDs Bus Receiver Module Cables and TerminationBus Receiver Module Status LEDs Genius Bus Controller Location of GBCs and BlocksSingle Bus Genius Networks Dual Bus Genius NetworksBus Controller LEDs One Application Program in Both PLCs Configuration RequirementsProgrammer Connection for Configuration Program Folders in Control Programming SoftwareCPU Configuration Parameters Program Folders in LogicmasterConfiguring Shared I/O References Parameter Default Range DescriptionFinding the Memory Available for Application Program Storage System Communications Window ConsiderationsRack Module Configuration Parameters Bus Controller Configuration ParametersGenius I/O Block Configuration Parameters Normal Operation Powerup of a Redundant CPU Incompatible Configurations Resynchronization of a Redundant CPUGHS Control Strategy GDB Control StrategyReferences for CPU Redundancy Ovrpre %S Reference Not AvailableScan Synchronization Sweep Time SynchronizationOutput Data Transfer to the Backup Unit AT aData Transfer Time Fail Wait TimeGFK-1527A Normal Operation Programming a Data Transfer from Backup Unit to Active Unit Data Transfer ExampleDisabling Data Transfer Copy in Backup Unit Svcreq #43 Command Block for Svcreq #43 Backup Qualification with Svcreq #43 Validating the Backup PLCs Input ScanValidating the Backup PLCs Logic Solution Switching Control to the Backup Unit Switching TimesRUN Disabled Mode RUN Disabled Mode for GHS Control StrategyExample 1 Role switches allowed on both units Example 2 Role switches allowed on both units Example 3 Role switches not allowed on either unitExample 4 Role switches allowed on both units Backup Active RUN Disabled Mode for GDB Control Strategy Example 8 InvalidFinding the Words to Checksum Each Sweep CGR772 CGR935Finding the Background Window Time Finding the Total Sweep TimeTimed Contacts Timer and PID Function BlocksMiscellaneous Operation Information Multiple I/O Scan SetsDebugger Stop to RUN Mode TransitionSequential Function Chart Programming SFC Background Window TimeGenius Bus Controller Switching Ethernet Global Data in a Redundancy CPU Ethernet Global Data ConsumptionEthernet Global Data Production Sntp TimestampingFault Detection Configuration of Fault ActionsFault Detection PLC Fault Table Messages for Redundancy Message Fault Description Corrective ActionWith redundancy in other fault groups Fault Response Faulting the Redundancy Communications Module Losing a LinkFault Actions in a CPU Redundancy System Configurable Faults Fault Group Type DescriptionNon-Configurable Fault Group Fatal Faults on Both Units in the Same SweepOn-Line Repair On-Line Repair Recommendations Power SupplyMaintaining Parallel Bus Termination RacksCentral Processor Unit Redundancy Communications Module and CablesRedundancy Communications Link Failures Genius Bus Controller Single Bus Networks Bus faultsBus Transmitter Module Genius BusDual Bus Networks Genius BlocksIC690CBL714A Multi-drop Cable SpecificationsCabling Information PurposeConnector a Connector A, 15-pin Female Battery connectors Bus Controller, Genius IndexIndex Online programming Online repair Svcreq
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