GE 90-70 manual Connectors, Bus Controller LEDs

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30.Data from Serial Bus Address 31 in the Primary PLC is the "preferred" data. The GDB control strategy must be used and all redundant Genius outputs must be transferred from the active to the backup unit.

Each dual bus can have up to 30 additional Genius devices connected to it. One Serial Bus Address must be reserved for a Hand-Held Monitor. Any type of Genius device can be connected to this bus. A Genius I/O device will use outputs from Serial bus Address 31 in preference to data from Serial bus Address 30. Outputs are determined by the Active Unit regardless of which bus controller provides the outputs since all redundant Genius outputs must be transferred from the active to the backup unit.

As a safety feature, a watchdog timer protects each Genius I/O link. The bus controller periodically resets this timer. If the timer ever expires, the bus controller stops functioning and its Channel OK LED turns off. If this happens in a Dual Bus Genius network of a CPU Redundant system, the paired GBC in the remote CPU drives the Genius I/O blocks. If the remote unit GBC is not available, the BSMs switch busses and use outputs from the other bus. The cause of the failure must be remedied to re-establish communications.

Connectors

The Bus Controller has a nine-pin connector for a Hand-Held Monitor. Bus connections are made to a removable terminal board.

Bus Controller LEDs

The GBC has three LEDs; the bottom one is not used.

Module OK: The top LED is ON when the board has successfully completed the power-up diagnostics. If the power- up diagnostics detect a failure or if the board fails during operation, the LED goes OFF. The LED blinks during the power-up diagnostics.

LEDs

MODULE OK

CHANNEL 1 OK

NOT USED

Hand-held

Monitor

Connector

Bus

Terminals

CH 1 OK: The CH 1 OK LED is ON after the board has

successfully completed the power-up diagnostics and OFF if a failure has been detected during the power-up diagnostics or if its bus or bus controller fails while the CPU is running (even in the STOP mode). If the bus controller fails the LED remains off. For a bus failure, such as a broken wire or excessive bus errors, the LED remains off until the failure condition is corrected.

The LED also remains OFF until its serial bus address is configured.

2-12 Series 90™-70 Enhanced Hot Standby CPU Redundancy User's Guide – May 2000 GFK-1527A