OperShelve
The alarm instruction only processes the OperShelve tag on transition from cleared to set to prevent unwanted reshelving of the alarm. For example, if an operator presses a push button to shelve the alarm while the ProgUnshelve tag is set, the alarm is not shelved because the ProgUnshelve tag takes precedence. To shelve the alarm, the operator can release and press the push button again once ProgUnshelve is cleared.
Affects Math Status Flags
| Controllers | Affected Math Status Flags |
| CompactLogix 5380, CompactLogix 5480, ControlLogix 5580, Compact GuardLogix 5380, and GuardLogix 5580 controllers | Conditional |
| CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, GuardLogix 5570 controllers | Yes |
| A minor fault will occur if: | Fault Type | Fault Code |
| The input value is INF or NAN for CompactLogix 5370, ControlLogix 5570, Compact GuardLogix 5370, GuardLogix 5570 controllers only. | 4 | 4 |
See ftath Status Flags.
