6.2.2 ST Language syntax

Serial number	Operator description	Symbol	Example	Precedence
1	Brackets	()	(A+B/C)	1(Highest)
2	Call a function with return value	Function name (parameter list)	MAX(X,Y)	2
3	Dereference	^	R^	3
4	One dollar off	-	-A	4
5	One dollar plus	+	+A	4
6	Negation (find the complement code)	NOT	NOT C	4
7	Power operation	**	A**B	5
8	Multiplication	*	A*B	6
9	Division	/	A/B	6
10	Modular operation	MOD	A MOD B	6
11	Addition	+	A+B+C	7
12	Subtraction	-	A-B-C	7
13	Compare sizes	< ≥	A<B	8
14	Comparison of equality	=	A=B	8
15	Is the comparison unequal	<>	A<>B	8
16	"AND" operation	& AND	A&B A AND B	9
17	"XOR" operation	XOR	A XOR B	10
18	"OR" operation	OR	A OR B	11

Expression: The expression will be evaluated during the execution of the program and then return a value. An expression consists of operands (constants, variables, constants, or function calls) and their matching operators (such as *, /, +, or -). Operators allow expressions to be joined together or nested within each other
The order of operations is the precedence of the relevant operators, the order from left to right, and the parentheses

An arithmetic expression can be either a numeric value or a combination of two values or expressions with arithmetic operators. Arithmetic expressions can handle various data types supported by the current CPU

The data types supported by arithmetic expressions are shown in the following table:

Operation	Operator	First operand	Second operand	Result
Power operation	**	Floating point number/integer //Base	Integer/Floating point number //Exponent	Floating point number
One dollar plus or one dollar minus	+ or -	integer/floating point number TIME/LTIME	-	integer/floating point number TIME/LTIME
Multiplication	*	Integer/Floating point number TIME/LTIME	Integer/Floating point number Integer	Integer/Floating point number TIME/LTIME
Division	/	Integer/Floating point number TIME/LTIME	Integer/Floating point number (not equal to 0) Integer	Integer/Floating point number TIME/LTIME
Modular operation	MOD	Integer	Integer	Integer
Addition or subtraction	+ or -	integer/floating point TIME LTIME TOD DATE DT LTOD LDATE<br/ >LDT	Integer/Floating point TI ME,DINT(INT,UINT,SINT,USINT) LTIME(TIME),LINT(DINT,UDINT,INT,UINT,SINT,USINT) TIME,DINT(INT,UINT,S INT,USINT) DINT(INT,UINT,SINT,USINT) DINT(INT,UINT,SINT,USINT) LTIME,LINT(DINT,UDINT,INT,UINT ,SINT,USINT) LINT(DINT,UDINT,INT,UINT,SINT,USINT) LTIME,LINT(DINT,UDINT,INT,UINT,SINT,USINT)	Integer/floating point TIME LTIME TOD DATE DT LTOD LDATE LDT
Subtraction	-	TOD DATE DT LTOD LDATE LDT	TOD DATE DT<br/ >LTOD LDATE,DATE LDT	TIME DINT DINT LTIME LINT LTINE

A relational expression compares the values or data types of two operands and returns a Boolean value. If the comparison is true, the result is TRUE otherwise FALSE
The data types supported by relational expressions are shown in the following table:

Operation	Operator	First operand	Second operand	Result
Comparison: Equal, not equal	=,<>	Integer/Floating point Bit string String TIME, LTIME Date and time	Integer/Floating point Bit string String TIME, LTIME Date and time	BOOL
Comparison: Less than, less than or equal to, greater than, greater than or equal to	<,≤,>,≥	Integer/floating point number Bit string String TIME, LTIME Date and time	Integer/floating point Bit string String TIME, LTIME Date and time	BOOL

When comparing floating-point numbers, specific data patterns for invalid floating-point numbers (NaN) that result in invalid operations (e.g., the square root of -1) are not comparable
STRING comparison compares UTF-8 encoded characters; WSTRING comparison compares UTF-16 encoded characters. During the comparison process, the length of the variable and the corresponding value of each character will be compared
Only two time data of the same data type can be compared. The system cannot compare invalid date and time data patterns
If two variables have the same structured data type, the values of the two structured operands can be compared (T3 supports this operation)
To compare two variables of ARRAY data type, the operator can only be "=" or "< >". And the following requirements must be met: (T3 supports this operation)
- The data types of the elements must be the same
- The dimensions of the two ARRAYs must be the same
- The number of elements in all dimensions must be the same, but the specific ARRAY limits (starting subscripts) do not need to be the same
- Supports STRUCT arrays, but does not support FB type arrays
2 bit string size comparisons, the comparison is the comparison of the size of the bit strings corresponding to positive integer values. The bitstring data type can be compared with positive integers. But comparison with negative numbers is not allowed

A logical expression consists of two operands and a logical operator (AND, OR, XOR) or negation operand (NOT)

warning

If both operands are of BOOL data type, the result of the logical expression is also of BOOL data type
If at least one of the two operands is a bit string, the result is a bit string and the result is determined by the type of the highest operand

The data types supported by logical expressions are shown in the following table:

Operation	Operator	First operand	Second operand	Result
Negation (reverse code)	NOT	BOOL bit string	- -	BOOL bit string
"AND" operation	AND or &	BOOL bit string	BOOL bit string	BOOL bit string
"OR" operation	OR	BOOL bit string	BOOL bit string	BOOL bit string
"XOR" operation	XOR	BOOL bit string	BOOL bit string	BOOL bit string

Untyped constants follow the implicit conversion of expression data types. When the constant is an integer, it can be followed by an integer variable or a floating-point variable (or a typed constant) Perform invisible transformation. The result of the operation is "strongly typed" (deterministic type)

Part	Meaning
Sidebar	User can set bookmarks and breakpoints in the sidebar
Line number	The line number is displayed to the left of the program code
Outline view	The corresponding code section will be highlighted in the outline view
Code area	In the code area, ST programs can be edited
Display of absolute operands	The symbolic operands assigned to absolute addresses are listed in this table

For basic ST programming instructions, please refer to Basic Instructions-ST
For ST programming system library instructions, please refer to System Library Description