GE GFK-0787B Noise Reduction Machine User Manual


 
4
4-21GFK-0787B Chapter 4 PLC Subsystem
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).