IEC 61131-1:2003

INTERNATIONAL IEC
STANDARD
61131-1
Second edition
2003-05
Programmable controllers –
Part 1:
General information
Automates programmables –
Partie 1:
Informations générales
Reference number
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INTERNATIONAL IEC
STANDARD
61131-1
Second edition
2003-05
Programmable controllers –
Part 1:
General information
Automates programmables –
Partie 1:
Informations générales
 IEC 2003  Copyright - all rights reserved
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– 2 – 61131-1  IEC:2003(E)
CONTENTS
FOREWORD . 3
INTRODUCTION .5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions. 7
4 Functional characteristics. 8
4.1 Basic functional structure of a programmable controller system . 8
4.2 Characteristics of the CPU function . 11
4.3 Characteristics of the interface function to sensors and actuators . 13
4.4 Characteristics of the communication function . 14
4.5 Characteristics of the human-machine interface (HMI) function. 14
4.6 Characteristics of the programming, debugging, monitoring, testing and
documentation functions . 14
4.7 Characteristics of the power-supply functions . 16
5 Availability and reliability . 16
Bibliography . 18
Figure 1 – Basic functional structure of a PLC-system. 8
Figure 2 – Programmable controller hardware model (from IEC 61131-5) . 9
Figure 3 – Typical interface/port diagram of a PLC-system (from IEC 61131-2) . 10
Table 1 – Summary of programmable functions. 12

61131-1  IEC:2003(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROGRAMMABLE CONTROLLERS –
Part 1: General information
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the IEC publishes International Standards. Their preparation is
entrusted to technical committees; any IEC National Committee interested in the subject dealt with may
participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization
for Standardization (ISO) in accordance with conditions determined by agreement between the two
organizations.
2) The formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an
international consensus of opinion on the relevant subjects since each technical committee has representation
from all interested National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61131-1 has been prepared by subcommittee 65B: Devices, of
IEC technical committee 65: Industrial-process measurement and control.
This second edition of IEC 61131-1 cancels and replaces the first edition published in 1992 and
constitutes a technical revision.
The text of this standard is based on the following documents:
FDIS Report on voting
65B/484/FDIS 65B/487/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
IEC 61131 consists of the following parts under the general title: Programmable controllers.
Part 1: General information
Part 2: Equipment requirements and tests
Part 3: Programming languages
Part 4: User guidelines
Part 5: Communications
Part 6: Reserved
– 4 – 61131-1  IEC:2003(E)
Part 7: Fuzzy-control programming
Part 8: Guidelines for the application and implementation of programming languages for
programmable controllers
The committee has decided that the contents of this publication will remain unchanged until 2007.
At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
A bilingual version of this standard may be issued at a later date.

61131-1  IEC:2003(E) – 5 –
INTRODUCTION
This Part of IEC 61131 constitutes Part 1 of a series of standards on programmable controllers
and their associated peripherals and should be read in conjunction with the other parts of the
series.
Where a conflict exists between this and other IEC standards (except basic safety standards),
the provisions of this standard should be considered to govern in the area of programmable
controllers and their associated peripherals.
The purposes of this standard are:
Part 1 establishes the definitions and identifies the principal characteristics relevant to the
selection and application of programmable controllers and their associated peripherals;
Part 2 specifies equipment requirements and related tests for programmable controllers (PLC)
and their associated peripherals;
Part 3 defines, for each of the most commonly used programming languages, major fields of
application, syntactic and semantic rules, simple but complete basic sets of programming
elements, applicable tests and means by which manufacturers may expand or adapt those
basic sets to their own programmable controller implementations;
Part 4 gives general overview information and application guidelines of the standard for the
PLC end-user;
Part 5 defines the communication between programmable controllers and other electronic
systems;
Part 6 is reserved;
Part 7 defines the programming language for fuzzy control;
Part 8 gives guidelines for the application and implementation of the programming languages
defined in Part 3.
– 6 – 61131-1  IEC:2003(E)
PROGRAMMABLE CONTROLLERS –
Part 1: General information
1 Scope
This Part of IEC 61131 applies to programmable controllers (PLC) and their associated peri-
pherals such as programming and debugging tools (PADTs), human-machine interfaces
(HMIs), etc., which have as their intended use the control and command of machines and
industrial processes.
PLCs and their associated peripherals are intended to be used in an industrial environment
and may be provided as open or enclosed equipment. If a PLC or its associated peripherals are
intended for use in other environments, then the specific requirements, standards and
installation practices for those other environments must be additionally applied to the PLC
and its associated peripherals.
The functionality of a programmable controller can be performed as well on a specific hardware
and software platform as on a general-purpose computer or a personal computer with industrial
environment features. This standard applies to any products performing the function of PLCs
and/or their associated peripherals. This standard does not deal with the functional safety or
other aspects of the overall automated system. PLCs, their application programme and their
associated peripherals are considered as components of a control system.
Since PLCs are component devices, safety considerations for the overall automated system
including installation and application are beyond the scope of this Part. However, PLC safety as
related to electric shock and fire hazards, electrical interference immunity and error detecting
of the PLC-system operation (such as the use of parity checking, self-testing diagnostics, etc.),
are addressed. Refer to IEC 60364 or applicable national/local regulations for electrical instal-
lation and guidelines.
This Part of IEC 61131 gives the definitions of terms used in this standard. It identifies the
principal functional characteristics of programmable controller systems.
2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 61131-2, Programmable controllers – Part 2: Equipment requirements and tests
IEC 61131-3:2003, Programmable controllers – Part 3: Programming languages
___________
To be published.
61131-1  IEC:2003(E) – 7 –
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
application programme or user programme
logical assembly of all the programming language elements and constructs necessary for the
intended signal processing required for the control of a machine or process by a PLC-system
3.2
automated system
control system beyond the scope of IEC 61131, in which PLC-systems are incorporated by or
for the user, but which also contains other components including their application programmes
3.3
field device
catalogued part to provide input and/or output interfaces or to provide data pre-
processing/post-processing to the programmable controller system. A remote field device may
operate autonomously from the programmable controller system. It can be connected to the
programmable controller using a field bus
3.4
ladder diagram or relay ladder diagram
one or more networks of contacts, coils, graphically represented functions, function blocks,
data elements, labels, and connective elements, delimited on the left and (optionally) on the
right by power rails
3.5
programmable (logic) controller (PLC)
digitally operating electronic system, designed for use in an industrial environment, which uses
a programmable memory for the internal storage of user-oriented instructions for implementing
specific functions such as logic, sequencing, timing, counting and arithmetic, to control,
through digital or analogue inputs and outputs, various types of machines or processes. Both
the PLC and its associated peripherals are designed so that they can be easily integrated into
an industrial control system and easily used in all the
...