Instruction List (IL)

A program written in IL language is a list of instructions. Each instruction is written on one line of text. An instruction may have one or more operands. Operands are variables or constant expressions. Each instruction may begin with a label, followed by the ":" character. Labels are used as destination for jump instructions.

The Workbench Studio allows you to mix ST and IL languages in textual program. ST is the default language. When you enter IL instructions, the program must be entered between BEGIN_IL and END_IL keywords, such as in the following example:

Example

BEGIN_IL
LD var1
ST var2
END_IL

Comments

Comment texts can be entered at the end of a line containing an instruction. Comment texts have no meaning for the execution of the program. A comment text must begin with "(*" and end with "*)". Comments may also be entered on empty lines (with no instruction), and on several lines (i.e. a comment text may include line breaks). Comment texts cannot be nested.

Data flow

An IL complete statement is made of instructions for:

first: evaluating an expression (called current result).
then: use the current result for performing actions.

Evaluation of expressions

The order of instructions in the program is the one used for evaluating expressions, unless parenthesis are inserted. Below are the available instructions for evaluation of expressions:

Instruction	Operand	Meaning
LD / LDN	any type	Loads the operand in the current result.
AND (&)	boolean	AND between the operand and the current result.
OR / ORN	boolean	OR between the operand and the current result.
XOR / XORN	boolean	XOR between the operand and the current result.
ADD	numerical	Adds the operand and the current result.
SUB	numerical	Subtract the operand from the current result.
MUL	numerical	Multiply the operand and the current result.
DIV	numerical	Divide the current result by the operand.
GT	numerical	Compares the result with the operand.
GE	numerical	Compares the result with the operand.
LT	numerical	Compares the result with the operand.
LE	numerical	Compares the result with the operand.
EQ	numerical	Compares the result with the operand.
NE	numerical	Compares the result with the operand.
Function call	func. arguments	Calls a function.
Parenthesis		Changes the execution folder.

Information

Instructions suffixed by N uses the boolean negation of the operand.

Actions

The following instructions perform actions according to the value of currrent result. Some of these instructions do not need a current result to be evaluated:

Instruction	Operand	Meaning
ST / STN	any type	Stores the current result in the operand.
JMP	label	Jump to a label - no current result needed.
JMPC	label	Jump to a label if the current result is TRUE.
JMPNC / JMPCN	label	Jump to a label if the current result is FALSE.
S	boolean	Sets the operand to TRUE if the current result is TRUE.
R	boolean	Sets the operand to FALSE if the current result is TRUE.
CAL	f. block	Calls a function block (no current result needed).
CALC	f. block	Calls a function block if the current result is TRUE.
CALNC / CALCN	f. block	Calls a function block if the current result is FALSE.

Information

Instructions suffixed by N uses the boolean negation of the operand.

Instruction List (IL)

IEC 61131-3 Automation platform > Programming - Reference guide > Programming languages - Overview > Instruction List (IL)

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