GE 90-70 manual Switching Control to the Backup Unit, Switching Times

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4

Switching Control to the Backup Unit

Control switches from the active unit to the backup unit if:

1. the active unit has a failure;

2. the pushbutton switch on the Redundancy Communications Module is pressed;

3. a switch is commanded from the application program.

4. the active unit is placed in Stop mode or powered off.

Switching Times

The amount of time needed to switch control from the active unit to the backup unit depends on the reason for the switch.

If the active PLC CPU fails or loses power, switching occurs after the backup unit determines that the active unit failed to rendezvous at the synchronization point. Failure to rendezvous may take up to 2 failwait timeouts (one for each link) to determine. Control does not transfer until both Redundancy Communications links have been tried unsuccessfully.

If the RCM switch is pressed, or if the application program commands a role switch (see below) or if the CPU detects a fault, the switch occurs at the start of the next sweep. The delay is up to 1 sweep. There may be an input and an output scan after fault detection. A control takeover due to failure or loss of power can occur at any time. However, a manual role switch may not occur within 10 seconds of a previous manual role switch.

Commanding a Role Switch from the Application Program (SVCREQ #26)

The application program can use SVCREQ #26 to command a role switch between the redundant CPUs (active to backup and backup to active). The switch occurs on the next sweep if the units are synchronized.

When SVCREQ #26 receives power flow to its enable input, the PLC is requested to perform a role switch. Power flow from SVCREQ #26 indicates that a role switch will be attempted on the next sweep. Power flow does not indicate that a role switch has occurred or that a role switch will definitely occur on the next sweep. The 10-second limitation allows these SVC_REQs to be in both units such that only a single switch occurs if the request is made by both units at approximately the same time. The PARM parameter is ignored by SVC_REQ #26; however the programming software requires that an entry be made for PARM. You can enter any appropriate reference here; it will not be used.

Example

In this example application, a switch on a control console is wired to input %I0001. In the program logic, the reference for %I0001 is used as the input to the SVCREQ #26 function block. When the switch is closed, logic power flows to SVCREQ #26, causing a role switch between the units.

%I00001

 

%M00001

 

 

SVC_

 

 

REQ

CONST

-

FNC

00026

 

 

%R00001

-

PARM

4-14

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

GFK-1527A

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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 Definition of Terms IntroductionEnhanced Hot Standby CPU Redundancy Compatibility with CPU780 Using the Redundancy CPU for Non-Redundant OperationDifferences in Operation for Redundancy CPUs Features not Available with Redundancy CPUsRedundancy CPUs as Compared to Other Series 90-70 CPUs Redundancy Communications Module Enhanced Redundancy CPU ModuleRedundant Racks Systems for Enhanced Hot Standby CPU RedundancyCable Connections Genius I/OLocal I/O Local I/0 Can be Enhanced Hot Standby CPU Redundancy System with Local I/OGDB Control Strategy Control StrategiesGHS Control Strategy Output Control with GDB Basic Enhanced Hot Standby OperationOutput Control with GHS 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 StrategyDuplex CPU Redundancy Online ProgrammingOn-Line Repair System Racks For Installation InstructionsSystem Components Redundancy CPU FeaturesExpansion Memory Board Watchdog TimerCPU Architecture Memory Protect Keyswitch CPU FeaturesBattery Connectors CPU LEDsPort CPU Mode SwitchUnit Select Pushbutton Redundancy Communications ModuleRCM Status Leds ConnectorBus Transmitter Module Status LEDs ConnectorsBus Transmitter Module Bus Receiver Module Status LEDs Bus Receiver ModuleCables and Termination Location of GBCs and Blocks Genius Bus ControllerDual Bus Genius Networks Single Bus Genius NetworksBus Controller LEDs Programmer Connection for Configuration Configuration RequirementsOne Application Program in Both PLCs Program Folders in Control Programming SoftwareProgram 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 Logic Solution Backup Qualification with Svcreq #43Validating the Backup PLCs Input Scan Switching Times Switching Control to the Backup UnitExample 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 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 TimeMiscellaneous Operation Information Timer and PID Function BlocksTimed Contacts Multiple I/O Scan SetsSequential Function Chart Programming SFC Stop to RUN Mode TransitionDebugger Background Window TimeGenius 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 Maintaining Parallel Bus Termination Power SupplyOn-Line Repair Recommendations RacksRedundancy Communications Link Failures Central Processor UnitRedundancy Communications Module and Cables Bus Transmitter Module Single Bus Networks Bus faultsGenius Bus Controller Genius BusGenius Blocks Dual Bus NetworksCabling Information SpecificationsIC690CBL714A Multi-drop Cable PurposeConnector a Connector A, 15-pin Female Index Battery connectors Bus Controller, GeniusIndex Online programming Online repair Svcreq
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