GE 90-70 manual GHS Control Strategy, GDB Control Strategy

Page 43

4

FST_EXE references for program blocks with the same name are transferred from the active to the backup CPU. The result is that if one CPU is already in Run mode and the other is transitioning to Run mode, the FST_SCN and matching FST_EXE bits are not set on the first scan of the transitioning unit. These bits are considered system bits and set if one unit comes up alone, or if both units come up together.

No transfer of data occurs at this point if both units are transitioning to Run mode. Instead, the normal clearing of non-retentive data happens and the FST_SCN and FST_EXE references are set as in the non-redundant CPU models.

The timer information and the FST_EXE %S reference bits are not continuously transferred. The timer information and FST_EXE references are transferred only at resynchronization time. Timer information is calculated each sweep from the universal Start of Sweep Time transferred every sweep.

GHS Control Strategy

In the GHS Control Strategy, the Primary Unit (with bus address 31), is always the preferred CPU. The Secondary Unit (with bus address 30) has outputs enabled to its Genius bus controllers at all times, whether it is in control or not. This is necessary to prevent glitching of the outputs when a switch occurs. The Primary Unit, on the other hand, must disable its outputs whenever control is manually switched to the Secondary Unit. The Primary Unit must re-enable its outputs if it is again selected as the active unit. Glitching of the outputs does not occur on a switch from the Secondary to the Primary Unit when it is done manually. However a glitch may occur if the switch is made automatically due to a failure in the Secondary Unit.

For this reason, the primary CPU should normally be selected as the active unit. Any time the Primary Unit transitions from STOP to RUN mode, the Primary Unit assumes control from the Secondary Unit after resynchronization. This is handled automatically by the CPU operating system.

The Primary Unit in the GHS Control Strategy becomes a functioning backup if control is manually switched to the Secondary Unit. After this happens, the Secondary Unit remains the active unit and the Primary Unit remains the backup until another manual switch is commanded, or until either unit transitions from STOP to RUN mode. A STOP to RUN mode transition always occurs when the unit is power cycled and proceeds directly to RUN mode or when commanded to transition by either the programmer or the toggle switch. A failure of the Secondary Unit while it is active may result in a glitch in the outputs.

GDB Control Strategy

Unlike the GHS Control Strategy, the GDB Control Strategy does not have a preferred unit. Outputs are always enabled for both units (unless explicitly disabled) so that bumpless switching is possible regardless of which unit is currently the active unit.

If both units power up together and go to RUN mode, the Primary Unit becomes the active unit and the Secondary Unit becomes the backup unit.

If one of the units is already in RUN mode and the other unit goes to RUN mode, then the unit already in RUN mode remains the active unit and the transitioning unit becomes the backup unit. The behavior is the same whether the unit going to RUN is the Primary Unit or the Secondary Unit.

If dual busses are configured, failure of one of the Genius trunk cables results in the blocks switching to the other bus. The bus can then be repaired. Failures of the Genius stub cables (the

4-4

Series 90™-70 Enhanced Hot Standby CPU Redundancy User's Guide – May 2000

GFK-1527A

Page 42 Page 44
Image 43
Page 42 Page 44
Contents GE Fanuc Automation GFL-002 Preface Content of This ManualRelated Publications Preface Contents Contents Chapter Fault Detection Appendix a Cabling Information Definition of Terms IntroductionEnhanced Hot Standby CPU Redundancy Compatibility with CPU780 Using the Redundancy CPU for Non-Redundant OperationRedundancy CPUs as Compared to Other Series 90-70 CPUs Features not Available with Redundancy CPUsDifferences in Operation for Redundancy CPUs Systems for Enhanced Hot Standby CPU Redundancy Enhanced Redundancy CPU ModuleRedundancy Communications Module Redundant RacksLocal I/O Genius I/OCable Connections Local I/0 Can be Enhanced Hot Standby CPU Redundancy System with Local I/OGHS Control Strategy Control StrategiesGDB Control Strategy Output Control with GHS Basic Enhanced Hot Standby OperationOutput Control with GDB Single Bus with Preferred Master GHS Control Strategy Basic CPU Redundancy SetupsCritical Data + Redundant Outputs Transferred Single Bus with Floating Master GDB Control StrategyPaired GBC = INT/EXT Internal External Dual Bus with Floating Master GDB Control StrategyOn-Line Repair Online ProgrammingDuplex CPU Redundancy System Components For Installation InstructionsSystem Racks Redundancy CPU FeaturesCPU Architecture Watchdog TimerExpansion Memory Board CPU LEDs CPU FeaturesMemory Protect Keyswitch Battery ConnectorsPort CPU Mode SwitchUnit Select Pushbutton Redundancy Communications ModuleRCM Status Leds ConnectorBus Transmitter Module ConnectorsBus Transmitter Module Status LEDs Cables and Termination Bus Receiver ModuleBus Receiver Module Status LEDs Location of GBCs and Blocks Genius Bus ControllerDual Bus Genius Networks Single Bus Genius NetworksBus Controller LEDs Program Folders in Control Programming Software Configuration RequirementsProgrammer Connection for Configuration One Application Program in Both PLCsProgram Folders in Logicmaster CPU Configuration ParametersParameter Default Range Description Configuring Shared I/O ReferencesSystem Communications Window Considerations Finding the Memory Available for Application Program StorageBus Controller Configuration Parameters Rack Module Configuration ParametersGenius I/O Block Configuration Parameters Normal Operation Powerup of a Redundant CPU Resynchronization of a Redundant CPU Incompatible ConfigurationsGDB Control Strategy GHS Control StrategyOvrpre %S Reference Not Available References for CPU RedundancySweep Time Synchronization Scan SynchronizationAT a Output Data Transfer to the Backup UnitFail Wait Time Data Transfer TimeGFK-1527A Normal Operation Data Transfer Example Programming a Data Transfer from Backup Unit to Active UnitDisabling Data Transfer Copy in Backup Unit Svcreq #43 Command Block for Svcreq #43 Validating the Backup PLCs Input Scan Backup Qualification with Svcreq #43Validating the Backup PLCs Logic Solution Switching Times Switching Control to the Backup UnitRUN Disabled Mode for GHS Control Strategy RUN Disabled ModeExample 1 Role switches allowed on both units Example 3 Role switches not allowed on either unit Example 2 Role switches allowed on both unitsExample 4 Role switches allowed on both units Backup Active Example 8 Invalid RUN Disabled Mode for GDB Control StrategyCGR772 CGR935 Finding the Words to Checksum Each SweepFinding the Total Sweep Time Finding the Background Window TimeMultiple I/O Scan Sets Timer and PID Function BlocksMiscellaneous Operation Information Timed ContactsBackground Window Time Stop to RUN Mode TransitionSequential Function Chart Programming SFC DebuggerGenius Bus Controller Switching Ethernet Global Data Consumption Ethernet Global Data in a Redundancy CPUSntp Timestamping Ethernet Global Data ProductionConfiguration of Fault Actions Fault DetectionFault Detection Message Fault Description Corrective Action PLC Fault Table Messages for RedundancyWith redundancy in other fault groups Fault Response Losing a Link Faulting the Redundancy Communications ModuleFault Actions in a CPU Redundancy System Fault Group Type Description Configurable FaultsFatal Faults on Both Units in the Same Sweep Non-Configurable Fault GroupOn-Line Repair Racks Power SupplyMaintaining Parallel Bus Termination On-Line Repair RecommendationsRedundancy Communications Module and Cables Central Processor UnitRedundancy Communications Link Failures Genius Bus Single Bus Networks Bus faultsBus Transmitter Module Genius Bus ControllerGenius Blocks Dual Bus NetworksPurpose SpecificationsCabling Information IC690CBL714A Multi-drop CableConnector a Connector A, 15-pin Female Index Battery connectors Bus Controller, GeniusIndex Online programming Online repair Svcreq
Top Page Image Contents