Truncate (TRUNC)
When enabled, the TRUNC instruction removes (truncates) the fractional part of the Source and stores the result in the Destination.
Truncating does not round the value; rather, the non-fractional part remains the same, regardless of the value of the fractional part.
Available Languages
Ladder Diagram
Structured Text
This instruction is not available in structured text. However, in the Structured Text
Editor you can use TRUNC as an operator in an expression to compute the same result. Refer
to Structured Text syntax for more information on the syntax of
expressions and assignments within structured text.
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.
There are data conversion rules for mixing numeric data types within an instruction. See Data conversions.
Ladder Diagram
Operand | Data Type | Format | Description |
|---|---|---|---|
Source | REAL LREAL | immediate tag | Value to truncate. |
Destination | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | tag | Tag to store the result of the instruction. |
Affects Math Status Flags
Conditional. See Math status flags.
Major/Minor Faults
Execution
Ladder Diagram
Condition/State | Action Taken |
|---|---|
Prescan | N/A. |
Rung-condition-in is false | Set Rung-condition-out to Rung-condition-in. |
Rung-condition-in is true | Set Rung-condition-out to Rung-condition-in. Dest = Truncated value of the Source. |
Postscan | N/A. |
Examples
Ladder Diagram
Structured Text
DINT_dest := TRUNC(REAL_src);
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