One Shot Falling (OSF)
This information applies to the
CompactLogix
5370, ControlLogix
5570, Compact GuardLogix
5370, GuardLogix
5570, Compact GuardLogix
5380, CompactLogix
5380, CompactLogix
5480, ControlLogix
5580, and GuardLogix
5580 controllers.The One Shot Falling (OSF) instruction sets the output bit for one scan when rung-condition-in transitions from true to false.
Available Languages
Ladder Diagram
Operands
IMPORTANT:
Unexpected operation may occur if:
- Output tag operands are overwritten
- Members of a structure operand are overwritten
- Except when specified, structure operands are shared by multiple instructions.
Ladder Diagram
Operand | Data Type | Format | Description |
|---|---|---|---|
Storage Bit | BOOL | tag | Stores the rung-condition-in from when the instruction was last executed. There are various operand addressing modes possible for the storage bit, see Bit Addressing for examples. |
Output Bit | BOOL | tag | Bit to be modified. |
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. See Index through arrays for array-indexing faults.
Execution
Ladder Diagram
Condition/State | Action Taken |
|---|---|
Prescan | The storage bit is cleared to false to prevent an invalid trigger during the first program scan. The output bit is cleared to false. |
Rung-condition-in is false | Set Rung-condition-out to Rung-condition-in. See OSF Flow Chart (False). |
Rung-condition-in is true | Set Rung-condition-out to Rung-condition-in. The storage bit is set to true. The output bit is cleared to false. |
Postscan | N/A |
OSF Flow Chart (False)
Example
Ladder Diagram
This example shows how an OSF can be used to make one or more instructions edge-triggered. Each time Limit_Switch_01 transitions from true to false the OSF will set Output_bit_02 to true. Any instruction conditioned by Output_bit_02 will be enabled and, since Output_bit_02 is only true for one scan, will execute once per transition.
Provide Feedback