ST Expressions An expression is a construct that returns a value following its evaluation. Expressions consist of operators and operands. In Extended Structured Text (ExST) , you can also use assignme

Assignments :

ST Assignment Operator Syntax: <operand> := <expression> This assignment operator executes the same function as the MOVE operator. :

ST Assignment Operator for Outputs The assignment operator => assigns the output of a function, a function block, or a method to a variable. The position on the right side of the operator can also be

ExST Assignment: S= When the operand of the Set assignment switches to TRUE , then TRUE is assigned to the variable to the left of the operator. The variable is set. <variable name> S= <operand name>

ExST Assignment: R= When the operand of the Reset assignment switches to TRUE , then FALSE is assigned to the variable to the left of the operator. The variable is reset. <variable name> R= <operand n

ExST Assignment as An Expression In ExST , as an extension to the IEC 61131-3 standard, CODESYS permits the use of assignments as expressions. Example 57 . Examples int_var1 := int_var2 := int_var3 +

Assignment Operator: REF= The operator generates a reference (pointer) to a value. Syntax: <variable name> REF= <variable name> ; Example 58 . Example refA : REFERENCE TO DUT; B : DUT; C : DUT; A REF=

Statements :

ST Statement: IF The IF statement is used for checking a condition and, depending on this condition, for executing the subsequent statements. A condition is coded as an expression that returns a Boole