3 control restart, The software model – Lenze DDS v2.0 User Manual

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Introduction to IEC 61131-3 programming

The software model

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DDS-IEC61131 EN 2.0

Overview: IEC 61131-3 standard operators

Arithmetic operators
ADD

Addition

MUL

Multiplication

SUB

Subtraction

DIV

Division

MOD

Remainders

EXP

Exponentiation

MOVE

Assignment

Bit-shift operators
SHL

Shift to LHS

SHR

Shift to RHS

ROR

CW rotation

ROL

CCW rotation

Bit-string operators
AND

Bit-by-bit AND of bit operands

OR

Bit-by-bit OR of bit operands

XOR

Bit-by-bit XOR of bit operands

NOT

Bit-by-bit NOT of bit operands

Selection operators
SEL

Binary selection

MAX

Maximum

MIN

Minimum

LIMIT

Limit

MUX

Multiplexer

Comparison operators
GT

Higher than

LT

Lower than

LE

Lower or equal

GE

Higher or equal

EQ

Equal

NE

Not equal

2.3

Control restart

The software model of IEC 61131-3 also defines the restart behaviour of the control.

Cold start

With cold starts, the program is loaded again. All variables are reset to their initial value. They either
use a standard initial value (e.g. 0 or FALSE) or the initial value indicated in the variable declaration
(optionally). All tasks of the resource are started.

Warm start

With warm starts (restarts), variables are not set to their inital value but continue with the value saved
before the interruption.

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