TO_LREAL block
Short summary
Name |
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→POU type |
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Category |
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Conform to →IEC-standard |
currently restricted and implementer-specific realization; see "Functionality" and more possible than defined in IEC-standard; see "Explicit conversion according to IEC-standard" |
Graphical interface |
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Available since |
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Functionality
The blocks serves for explicitly converting the value connected to input IN
into a value of data type LREAL
.
If the connected value is within the range of values overlapping for the data type of the input and for the result value LREAL
, the blocks returns this value.
Deviation from IEC-standard The IEC-standard defines that the conversion for the data types as defined by the IEC-standard is done as a binary transfer. However, this block deviates from the IEC-standard. The values of the data type
|
Observe as well:
-
If a value with more than 15 digits is converted, the result might be inexact. The reason is the number of significant digits of
LREAL
(details: see "Supported data types (in ST)" the note 3 and the note 4 after the table). -
If a value of data type
STRING
is connected to the input and this value is a valid real literal (see the following table for examples), the value is converted accordingly. In this case, the outputENO
is set to valueTRUE
.
In case of other values, the block returns the value0.0
. In this case, the outputENO
is set to valueFALSE
. Special case: If the connected value starts with a valid real literal and other characters follow (egB. '3.14159_26'
,STRING#'1.5 E10'
,'-INFxxx'
), the block returns the starting value as it is supported (hence:3.14159
,1.5
,-INF
) and the outputENO
is set to valueFALSE
.Description
Examples for values of data type
STRING
that correspond to a valid real literalsReal literal
'0', '0.0', '0.4560', '3.1415926', '-123456789',
STRING#'0', STRING#'0.0', STRING#'0.4560', STRING#'3.1415926', STRING#'-123456789'
Real literal with exponent
'-1.34E-12', '-1.34e-12', '1.0E+6', '1.0e+6, 1E+6', '1.234E6', '1.234e6',STRING#'-1.34E-12', STRING#'-1.34e-12', STRING#'1.0E+6', STRING#'1.0e+6, STRING#1E+6', STRING#'1.234E6', STRING#'1.234e6',' 987e-3', ' +2.5E30',STRING#' 987e-3', STRING#' +2.5E30'
"Not a Number" or infinite
'Nan', 'INF', '-INF'
Typed real literals (specifying the type
REAL
orLREAL
) are invalid real literals.
Examples for values of data typeSTRING
that correspond to an invalid real literal:'REAL#0.0'
or'LREAL#0.0'
-
If a value of data type
CHAR
is connected to the input and this value is a valid real literal (e.g.'0'
,CHAR#'9'
), the value is converted accordingly (hence:0.0
,9.0
). In this case, the outputENO
is set to valueTRUE
.
In case of other values (e.g.'+'
,CHAR#A
) , the block returns the value0.0
. In this case, the outputENO
is set to valueFALSE
.
Explicit conversion according to IEC-standard
The IEC-standard defines an explicit conversion of the following data types to LREAL
:
REAL
, LINT
, DINT
, INT
, SINT
, ULINT
, UDINT
, UINT
, USINT
, LWORD
The IEC-standard (Edition 3.0) defines a binary transfer for all data types of the input. But contrary to this, the appropriate value is converted according to the IEC-standard (Edition 2.0) for the following data types of the input.
LWORD
Details on the Neuron Power Engineer behavior of the block can be found in the section "Functionality".
Inputs, return value
|
Identifier |
Description |
|
---|---|---|---|
Inputs: |
|
|
value to be converted |
Return value: |
– |
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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.
Internal error diagnostic for block
The block checks the value connected to the input. The output ENO
of the block is set to value FALSE
(or an equivalent) in the following cases:
-
A
STRING
value contains an invalid character. (The value returned by the block depends on the position of the invalid characters. See the description under "Functionality" above.) -
A
CHAR
value contains an invalid character. (Moreover for this case, the block returns the value0.0
.)
Example for usage within ST-editor
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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.