One Shot Falling with Input (OSFI)
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 with Input (OSFI) instruction sets the OutputBit for one execution cycle when the InputBit toggles from false to true.
Available Languages
Ladder Diagram
This instruction is not available in ladder diagram.
Function Block
Structured Text
OSFI(OSFI_tag)
Operands
Structured Text
Operand | Type | Format | Description |
|---|---|---|---|
OSFI tag | FBD_ONESHOT | Structure | OSFI structure |
See Structured Text Syntax for operand-related faults
Function Block
Operand | Type | Format | Description |
|---|---|---|---|
OSFI tag | FBD_ONESHOT | Structure | OSFI structure |
FBD_ONESHOT Structure
Input Parameter | Data Type | Description |
|---|---|---|
EnableIn | BOOL | Enable input. If cleared, the instruction does not execute and outputs are not updated.
Default is set. |
InputBit | BOOL | Input bit. |
Output Parameter | Data Type | Description |
|---|---|---|
EnableOut | BOOL | Indicates if instruction is enabled. |
OutputBit | BOOL | Output bit |
Description
If InputBit is false, and it was true the last time the instruction was scanned then OutputBit will be set, otherwise OutputBit will be cleared.
Affects Math Status Flags
No
Major/Minor Faults
None specific to this instruction. See for operand-related faults.
Execution
Function Block
Condition / State | Action Taken |
|---|---|
Prescan | EnableIn and EnableOut bits are cleared to false. |
Tag.EnableIn is false | EnableIn and EnableOut bits are cleared to false. |
Tag.EnableIn is true | EnableIn and EnableOut bits are set to true. The instruction executes |
Instruction first run | N/A |
Instruction first scan | Previous InputBit history is cleared to require a True to False transition of InputBit. |
Postscan | EnableIn and EnableOut bits are cleared to false. |
Structured Text
Condition / State | Action Taken |
|---|---|
Prescan | See Prescan in the Function Block table. |
Normal execution | See Tag.EnableIn is true in the Function Block table. |
Postscan | See Postscan in the Function Block table. |
Example
When limit_switch1 goes from set to cleared, the OSFI instruction sets OutputBit for one scan.
Function Block
Structured Text
OSFI_01.InputBit := limit_switch1;
OSFI(OSFI_01);
Output_state := OSFI_01.OutputBit;
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