LT block

Short summary

Name	`LT`
→POU type	→function
Category	Standard (safe), Compare
Conform to →IEC-standard	currently restricted (IEC demands data type `ANY_ELEMENTARY` for the inputs, hence the following data types are demanded as well: `LTIME`, `STRING`, `WSTRING`, `CHAR`, `WCHAR`, `LDATE_AND_TIME`, `LTIME_OF_DAY` and `LDATE`. Currently, these data types are not supported for the block.)
Graphical interface
Available since	version 1.0.0 (for Neuron Power Engineer) for inputs with `ANY_NUM` Version 1.19.0 (for Neuron Power Engineer) for inputs with `ANY_ELEMENTARY`, but without `STRING` and `CHAR` version 3.8.0 (for library `Standard (safe)`): block provided in this library

Functionality

The block is a comparator regarding increasing sequence ("Less Than").

Enter the values at the inputs, those values are to be compared. The block returns value TRUE (or an equivalent), if a value connected to an input is less than the value connected to the respectively following input – hence, if: (IN1<IN2) & (IN2<IN3) & ... & (IN15<IN16)

Bitstring values (= ANY_BIT values; see →generic data type} are treated like unsigned →integer values by the block. This behavior is a specification according to the →IEC-standard.

Inaccuracies for floating-point numbers

Due to the internal representation of floating-point numbers (affects the data types REAL and LREAL) there might be inaccuracies when processing such values. Such inaccuracies might result in a not expected result when comparing such values.

Inputs, return value


Inputs:	`IN1`	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT`, `LINT`, `TIME`, `BOOL`, `BYTE`, `WORD`, `DWORD`, `LWORD`, `DATE_AND_TIME`, `DATE` or `TIME_OF_DAY`	1st value
	`IN2`	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT`, `LINT`, `TIME`, `BOOL`, `BYTE`, `WORD`, `DWORD`, `LWORD`, `DATE_AND_TIME`, `DATE` or `TIME_OF_DAY`	2nd value
	... (extensible until)
	`IN16`	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT`, `LINT`, `TIME`, `BOOL`, `BYTE`, `WORD`, `DWORD`, `LWORD`, `DATE_AND_TIME`, `DATE` or `TIME_OF_DAY`	16th value
Return value:	–	`BOOL`

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

See:

"Blocks for safe logic" whether this block is supported for developing safety-relevant applications.
"Highlighting safe logic in the FBD-editor" for the effects when using the block as a block for safe logic.

Example for usage within ST-editor

PROGRAM Test

VAR

        result : BOOL;

    END_VAR

    result := LT(IN1 := 1.0, IN2 := 2.0, IN3 := 1.0);     (* The variable 'result' evaluates to 'FALSE'. *)

    result := LT(IN1 := 1.0, IN2 := 2.0, IN3 := 3.0);     (* The variable 'result' evaluates to 'TRUE'.  *)

END_PROGRAM

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.