GE GFK-0787B user manual Shut Down Prevention, Shut Down Recovery

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I/O Shut Down Prevention

If an I/O fault causes an I/O shutdown to initiate, there is up to 16 hours of time to repair the fault and put the block(s) back into operation before the shutdown occurs. When the next autotest occurs on the PLC(s) that started its shutdown timer, that PLC automatically cancels its I/O shutdown (If the autotest is executed without faults on the affected block(s) before the actual shut down occurs). This autotest can be one that occurs automatically as specified by the configured autotest interval, or one that is initiated manually via the GMR control bit Autotest Manual Initiate (%M12260 ± ATMANIN). To clear any standing faults at the block(s) and in the I/O fault table of the PLCs, an I/O fault reset should be executed by turning on GMR Control bit %M12258 (IORES). Also note that at any time the Cancel I/O Shutdown (%M12265 ± SD_CAN) bit can be used to prevent the shutdown from occurring.

I/O Shut Down Recovery

If an I/O shutdown is allowed to complete, the affected I/O is set to its safe state.

Recovery from an I/O shutdown is accomplished with the following steps:

1)Repair the fault that caused the I/O shutdown to initiate. This may require simply replacing a blown fuse which had supplied power to a block, or replacing a damaged or failed block or repairing field wiring.

2)Initiate an I/O autotest in each of the three PLCs so that the PLC(s) can determine that the block(s) is repaired and again functioning properly. The autotest has to be executed at the PLCs which had actually started and expired their shutdown timers. The autotests can be those that occur automatically as specified by the configured autotest interval, or initiated manually via the GMR control bit Autotest Manual Initiate (%M12260 ± ATMANIN).

3)In the case of a block being powered off or replaced, a shut down of outputs the output block(s) may require a force logon to get them to accept output data from the CPUs. This can be done by using the GMR control bit %M12263 (FORCLOG).

4)To clear any standing faults at the block(s) and in the I/O fault table of the PLCs, an I/O Fault Reset should be executed by turning on GMR Control bit %M12258 (IORES).

GFK-0787B Chapter 4 PLC Subsystem 4-21