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 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 standard describes different literal types, according to the standard data types.
In EcoStruxure Machine Expert - Safety, literals can be inserted in code worksheets, variables worksheets (as initial value), and worksheets in debug mode when forcing or overwriting variables. Two basic literal types are supported with some restrictions concerning the IEC 61131-3 (also refer to the note below):
Numeric literals for the representation of numeric values
Duration literals for defining time data strings
When entering numeric and duration literals, underscores can be used to simplify the readability. Literals are not case-sensitive.
NOTE:
Literals must always be entered including the data type (e.g., BYTE#1, SAFEINT#1000).
Exceptions:
TRUE and FALSE are always handled as BOOL.
SAFETRUE and SAFEFALSE are always handled as SAFEBOOL.
"Standard" INT constants can also be entered without data type (e.g., 1000 means INT#1000) as decimal inputs are automatically interpreted as INT. Exception: 0 and 1 if used with Boolean data type.
In EcoStruxure Machine Expert - Safety, literals can be used with the following IEC 61131-3 data types and special safety-related data types:
BOOL/SAFEBOOL
BYTE/SAFEBYTE
WORD/SAFEWORD
DWORD/SAFEDWORD
INT/SAFEINT
DINT/SAFEDINT
TIME/SAFETIME
NOTE:
Special case: global variable acts as global constant.
If a global symbolic variable gets an initial value, it can be considered as a global constant with symbolic name. The initialized global symbolic variable is write-protected and the compiler treats it as a constant. As a result, it can be connected, for example, to a function block formal parameter which expects a constant.
Refer to the topic "Inserting Constants".
The following numeric literals can be used in EcoStruxure Machine Expert - Safety:
|
Type |
Examples |
|
Integer literals |
-12, 0, 123_456, +986 Refer to the first note below this table. |
|
Base 2 literals |
INT#2#1111_1111 Refer to the first note below this table. |
|
Base 8 literals |
INT#8#377 |
|
Base 16 literals |
INT#16#F0F0 |
|
Boolean FALSE and TRUE |
FALSE, TRUE andSAFEFALSE, SAFETRUE |
|
Boolean 0 and 1 |
0, 1 |
Typed numeric literals can be displayed on base of 2, 8 or 16 (see table above).
NOTE:
According to the IEC 61131-3, table 5, the "_" character can be used to improve the readability of literals.
NOTE:
The character "." (dot) is not allowed in numeric literals.
Duration data can be represented in hours, minutes, seconds, milliseconds, and in combination of these formats:
|
Type |
Examples |
|
Long prefix |
TIME#14mstime#14msSAFETIME#25h_15msafetime#25h_15m |
|
Short prefix NOTE: The short prefix representation is not allowed for SAFETIME literals. |
T#14mst#14mst#12m18s3.5msT#25h_15m t#25h_15m |
NOTE:
In duration literals, the character "." (dot) is only allowed for defining the smallest time unit to be displayed (e.g., TIME#12.3d, SAFETIME#1h12m4s3.5ms).
