STRING_TO Conversions

General Information

For general hints to be considered during type conversion, refer to the chapter Type Conversion Functions.

Definition

IEC operator for conversions from the variable type STRING to a different type.

Syntax

STRING_TO_<data type>

Specifying Values

Specify the operand of type STRING matching the IEC61131-3 standard. The value must correspond to a valid constant (literal) of the target type.

Convertible strings can contain:

  • Number with type prefix (example: '16#FFFFFFFF')

  • Number with grouping characters (example: '2#1111_1111')

    NOTE: Use the underscore, as the international weight and measure grouping character (thin space) is not permitted.

  • Floating-point number, also in exponential notation (example: '9.876' or '1.2E-34')

    NOTE: Floating-point numbers are not convertible. The comma is treated as a following character and therefore truncated.

  • Time, time of day, and date specification with prefix and size (example: 'T#2h', 'DT#2019-9-9-12:30:30.9')

  • Infinite values (example: '1.7E+400')

  • Additional character after a number (example: '2m' or '3.14') are truncated. Additional characters before a number are not permitted.

  • Spaces before (example: ' 3.14')

The operand must represent a valid value of the target data type.

NOTE: If the data type of the operand does not match the target type, or if the value exceeds the range of the target data type, then the result depends on the processor type and is therefore undefined.

Conversions from larger types to smaller types may result in loss of information.

 CAUTION
LOSS OF DATA
When converting mismatched data types or when the value being converted is larger than the target data type, be sure that the result is validated within your application.
Failure to follow these instructions can result in injury or equipment damage.

Example in IL

Example

Conversion result 

LD 'TRUE'
STRING_TO_BOOL
ST b

TRUE

Examples in ST

Example

Conversion result 

b := STRING_TO_BOOL('TRUE');

TRUE 

w := STRING_TO_WORD('abc34');

0 

w := STRING_TO_WORD('34abc');

34 

t := STRING_TO_TIME('T#127ms');

T#127ms 

r := STRING_TO_REAL('1.234');

1.234 

bv := STRING_TO_BYTE('500');

244

Example in FBD

Example

Conversion result

TRUE