Literals according to IEC 61131-3

Where constant numeric values, character strings or time data values are to be used in the code, for example, for connecting them to a formal parameter of a function/function block, literals can be used instead of constant variables. Literals are directly entered "hard-coded" constant values or strings. The IEC 61131-3 standard designates literals as "external representation of data". Literals can directly be entered in the code. It is not necessary to specify a declaration.

The IEC 61131-3 standard describes different literal types, according to the basic data types.

Furthermore, safety-related literals can be used according to the safety-related data types.

This topic contains the following sections:

Numeric literals

Type Examples

Integer literals -12 0 123_456 +986

Note
For SAFEINT literals, always the data type must be entered (SAFEINT#).

Real literals -12.0 0.0 0.4560 3.14159_26

Real literals with exponent -1.34E-12 -1.34e-12 1.0E+6

Long Real literals LREAL#-12.0
Observe the 2nd note below this table.

Long Real literals with exponent LREAL#2.3E-89
Observe the 2nd note below this table.

Base 2 literals INT#2#1111_1111

Base 8 literals INT#8#377

Base 16 literals INT#16#FF SINT#16#ff

Boolean FALSE and TRUE FALSE, TRUE
SAFEFALSE, SAFETRUE

Boolean 0 and 1 0, 1
For SAFEBOOL literals, always SAFEFALSE, SAFETRUE has to be used.

Note
INT literals can be used without keyword. Example: for INT#16#ff, you can use 16#ff.
BOOL/SAFEBOOL literals can also be used without keyword. Examples: for BOOL#FALSE, you can use FALSE and for SAFEBOOL#FALSE, you can use SAFEFALSE.

Note
If you are using PLCnext Engineer in another user interface language and/or with another Windows system locale than English you must enter numeric values with a '.' as decimal separator (always according to the English standard). This applies, for example, when entering initial values in variables tables or REAL/LREAL literals in the code.

Character string literals

Character string literals include single-byte or double-byte encoded characters.

A single-byte character string literal is a sequence of zero or more characters enclosed in single quote characters (''). A double-byte character string literal is a sequence of zero or more characters enclosed in double quote characters ("").

Type Examples

Single-byte character strings

Empty string ''

String with one space character ' '

Not empty string 'this is a text'

Double-byte character strings

Empty string ""

String with one space character " "

Not empty string "this is a text"

Type	Examples
Single-byte character strings
Empty string	''
String with one space character	' '
Not empty string	'this is a text'
Double-byte character strings
Empty string	""
String with one space character	" "
Not empty string	"this is a text"

Date and time literals

Duration data can be represented in hours, minutes, seconds, milliseconds and in combination of these formats.

Type Examples

Short prefix TIME data type: T#14ms t#14ms t#12m18s3.5ms T#25h_15m t#25h_15m

Note
The short prefix representation is not allowed for SAFETIME literals.

LTIME data type: LT#14ms t#14ms t#12m18s3.5ms T#25h_15m t#25h_15m

Long prefix TIME data type: TIME#14 ms time#14ms TIME#25h_15m time#25h_15m
SAFETIME data type: SAFETIME#14 ms safetime#14ms SAFETIME#25h_15m safetime#25h_15m
LTIME data type: LTIME#14 ms time#14ms TIME#25h_15m time#25h_15m

Further Info
See the section "Constant (Literal)" for information how to edit literals in the programming languages FBD/LD/SFC.