Operators
CODESYS V3 supports all IEC 61131-3 operators. These operators are recognized implicitly throughout the project. In addition to these IEC operators, CODESYS also supports some non-IEC 61131-3 operators.
Operators are used in blocks, such as functions.
Tip
For information about the processing order (binding strength) of the ST operators, see the "ST expressions" chapter.
Caution
For operations with floating-point data types, the computational result depends on the applied target system hardware.
Caution
For operations with overflow or underflow in the data type, the computational result depends on the applied target system hardware.
Overflow/underflow in the data type
The CODESYS compiler generates code for the target device and computes temporary results always with the native size that is defined by the target device. For example, computation is performed at least with 32-bit temporary values on x86 and ARM systems and always with 64-bit temporary values on x64 systems. This provides considerable advantages in the computation speed and often also produces the desired result. But this also means that an overflow or underflow in the data type is not truncated in some cases.
Example 1
The result of this addition is not truncated and the result in dwVar is 65536.
VAR wVar : WORD; dwVar: DWORD; END_VAR wVar := 65535; dwVar := wVar + 1;
Example 2
The overflow and underflow in the data type is not truncated and the results (bVar1, bVar2) of both comparisons are FALSE on 32-bit and 64-bit hardware.
VAR wVar1 : WORD; wVar2 : WORD; bVar1 : BOOL; bVar2 : BOOL; END_VAR wVar1 := 65535; wVar2 := 0; bVar1 := (wVar1 + 1) = wVar2; bVar2 := (wVar2 - 1) = wVar1;
Example 3
By the assignment to wVar3, the value is truncated to the target data type WORD and the result bvar1 is TRUE.
VAR wVar1 : WORD; wVar2 : WORD; wVar3 : WORD; bVar1 : BOOL; END_VAR wVar1 := 65535; wVar2 := 0; wVar3 := (wVar1 + 1); bVar1 := wVar3 = wVar2;
Example 4
In order to force the compiler to truncate the temporary results, a conversion can be inserted.
The type conversion makes sure that both comparisons are 16-bit only and the results (bVar1, bVar2) of both comparisons are each TRUE.
VAR wVar1 : WORD; wVar2 : WORD; bVar1 : BOOL; bVar2 : BOOL; END_VAR wVar1 := 65535; wVar2 := 0; bVar1 := TO_WORD(wVar1 + 1) = wVar2; bVar2 := TO_WORD(wVar2 - 1) = wVar1;
Arithmetic operators
Bitstring operators
Bitshift operators
Selection Operators
Comparison Operators
A comparison operator is a Boolean that compares two inputs (first and second operand).
Address operators
Call operators
Type conversion operators
You can explicitly call type conversion operators. The type conversion operators described below are available for typed conversions from one elementary type to another elementary type, as well as for overloading. Conversions from a "larger" type to a "smaller" type are also implicitly possible (for example, from INT to BYTE or from DINT to WORD).
Typed conversion: <elementary data type> _TO_ another elementary data type>
Overloaded conversion: TO_ <elementary data type>
Elementary Data Types
<elementary data type> = __UXINT | __XINT | __XWORD | BIT | BOOL | BYTE | DATE | DATE_AND_TIME | DINT | DT | DWORD | INT | LDATE | LDATE_AND_TIME | LDT | LINT | LREAL | LTIME | LTOD | LWORD | REAL | SINT | TIME | TOD | UDINT | UINT | ULINT | USINT | WORD
The keywords T, TIME_OF_DAY and DATE_AND_TIME are alternative forms for the data types TIME, TOD, and DT. T, TIME_OF_DAY and DATE_AND_TIME are not represented as a type conversion command.
Important
If the operand value for a type conversion operator is outside of the value range of the target data type, then the result output depends on the processor type and is therefore undefined. This is the case, for example, when a negative operand value is converted from LREAL to the target data type UINT.
Information can be lost when converting from larger data types to smaller data types.
String manipulation when converting to STRING or WSTRING
When converting the type to STRING or WSTRING, the typed value is left-aligned as a string and truncated if it is too long. Therefore, declare the return variable for the type conversion operators <>_TO_STRING and <>_TO_WSTRING long enough that the string has enough space without any manipulation.
Numeric Operators
Namespace operators
Namespace operators are extended from IEC 61131-3 operators. They make it possible for you to provided unique access to variables and modules, even when you use the same name multiple times for variables or modules in a project.
Multicore operators
Working with different tasks requires the synchronization of these tasks. This is especially true when working on multicore platforms. CODESYS provides some special operators to support this synchronization.
These operators are extensions of IEC-61131-3. The operators TEST_AND_SET and __COMPARE_AND_SWAP are used for similar tasks.