GE 90-70 manual Disabling Data Transfer Copy in Backup Unit Svcreq #43

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Disabling Data Transfer Copy in Backup Unit (SVCREQ #43)

Service Request function block #43 can be used on the backup to allow the backup unit to bypass the copy of the shared I/O data from the active unit. This function can be used to help determine if the active and backup CPUs are arriving at the same results.

This function is useful only when issued in the backup CPU. It is ignored if issued when the units are not synchronized, or if it is issued in the active unit.

SVCREQ #43 disables the copy of data for 1 sweep beginning with the output data transfer and ending with the input data transfer of the next sweep. The copy can be disabled for multiple sweeps by invoking SVCREQ #43 once each sweep for the appropriate number of sweeps.

The special resynchronization data transfer always occurs, even if SVCREQ #43 is invoked in the first sweep after synchronization (this data transfer includes all shared inputs, all shared outputs, and internal data which must be exchanged) since the resynchronization data transfer occurs before the start of logic execution.

This function can be set up to disable the copies for all transfers or just the output transfers. If just the output copy is disabled, the two units can still use the same set of inputs on each unit. This makes it possible to test the ability of the two units to derive the same results from the same inputs.

In all cases, the configured data transfers are still transferred over the Redundancy Communications Module / Bus Transmitter Module link every sweep and the rendezvous points are still met. The effect of SVCREQ #43 is to disable the copy of the data from the transfer to the actual reference memories configured.

Warning

When SVCREQ #43 is in effect, the backup unit will still take control of the system in event of a failure or role switch. Switches to the backup unit may cause a glitch (momentary interruption of data) of the outputs since the two units may not be generating the exact same results.

Consider disabling outputs on the backup unit while SVCREQ #43 is in effect. Disabling outputs on the backup unit eliminates the risk of an unsynchronized switch of control (which can cause a glitch in the outputs) if the active unit fails or loses power while the input/output copies are disabled. However, if the active unit does fail or loses power while outputs are disabled on the backup unit, the system's outputs will go to their default settings. A secondary effect of disabling outputs on the backup unit is that the unsynchronized fault action table is used by the active unit to determine which faults are fatal.

Note

If the CPU is already in RUN/ENABLED mode, a command to disable its outputs will not take effect until one sweep after the command is received. Therefore, disable the outputs at least one sweep before you enable SVCREQ #43.

SVCREQ #43 can be used with both the GHS and the GDB Control Strategies. However, with the GDB Control Strategy, it cannot be used to disable output data transfer on the Primary unit when outputs are enabled on the Primary Unit. If that is attempted, the function block is rejected.

GFK-1527A

Chapter 4 Normal Operation

4-11

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Contents GE Fanuc Automation GFL-002 Related Publications Content of This ManualPreface 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 CPU780Differences in Operation for Redundancy CPUs Features not Available with Redundancy CPUsRedundancy CPUs as Compared to Other Series 90-70 CPUs Redundant Racks Enhanced Redundancy CPU ModuleRedundancy Communications Module Systems for Enhanced Hot Standby CPU RedundancyCable Connections Genius I/OLocal I/O Enhanced Hot Standby CPU Redundancy System with Local I/O Local I/0 Can beGDB Control Strategy Control StrategiesGHS Control Strategy Output Control with GDB Basic Enhanced Hot Standby OperationOutput Control with GHS 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 ExternalDuplex CPU Redundancy Online ProgrammingOn-Line Repair System Racks For Installation InstructionsSystem Components Features Redundancy CPUExpansion Memory Board Watchdog TimerCPU Architecture Battery Connectors CPU FeaturesMemory Protect Keyswitch CPU LEDsCPU Mode Switch PortRedundancy Communications Module Unit Select PushbuttonConnector RCM Status LedsBus Transmitter Module Status LEDs ConnectorsBus Transmitter Module Bus Receiver Module Status LEDs Bus Receiver ModuleCables and Termination 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 a Data 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 Validating the Backup PLCs Logic Solution Backup Qualification with Svcreq #43Validating the Backup PLCs Input Scan Switching Control to the Backup Unit Switching TimesExample 1 Role switches allowed on both units RUN Disabled ModeRUN Disabled Mode for GHS Control Strategy Example 4 Role switches allowed on both units Example 2 Role switches allowed on both unitsExample 3 Role switches not allowed on either unit 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 RacksRedundancy Communications Link Failures Central Processor UnitRedundancy Communications Module and Cables 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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