1.1 General

This standard is one of a series produced to facilitate the interconnection of automation system components. It is related to other standards in the set as defined by the three-layer fieldbus reference model described in IEC/TR 61158-1:2010.

This standard contains material specific to the Type 21 communication protocol.

1.2 Overview

The Fieldbus Application Layer (FAL) provides user programs with a means to access the fieldbus communication environment. In this respect, the FAL can be viewed as a window between corresponding application programs.

This standard provides common elements for basic time-critical and non-time-critical messaging communications between application programs in an automation environment, as well as material specific to Type 21. The term “time-critical” is used to represent the presence of a time-window, within which one or more specified actions must to be completed with some defined level of certainty. Failure to complete specified actions within the required time risks the failure of the applications requesting the actions, with attendant risk to equipment, plant, and possibly human life.

This standard defines interactions between remote applications. It also defines the externally visible behavior provided by the Type 21 application layer in terms of:

the formal abstract syntax defining the application layer protocol data units (APDUs) conveyed between communicating application entities;
the transfer syntax defining encoding rules that are applied to the APDUs;
the application context state machine defining the application service behavior visible between communicating application entities;
the application relationship state machines defining the communication behavior visible between communicating application entities.

The purpose of this standard is to:

describe the wire-representation of the service primitives defined in IEC 61158-5-21:2010;
describe the externally visible behavior associated with their transfer.

This standard defines the protocol of the Type 21 application layer in conformance with the OSI Basic Reference Model (ISO/IEC 7498) and the OSI application layer structure (ISO/IEC 9545).

1.3 Specifications

The principal objective of this standard is to specify the syntax and behavior of the application layer protocol that conveys the Type 21 application layer services.

A secondary objective is to provide migration paths from previously existing industrial communications protocols.

1.4 Conformance

This standard does not restrict individual implementations or products, nor does it constrain the implementations of application layer entities in industrial automation systems. Conformance is achieved through implementation of this application layer protocol specification.

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PDF Pages	PDF Title
6	CONTENTS
9	INTRODUCTION
10	1 Scope 1.1 General 1.2 Overview
11	1.3 Specifications 1.4 Conformance 2 Normative references
12	3 Terms, definitions, symbols, abbreviations, and conventions 3.1 Terms and definitions from other ISO/IEC standards 3.2 Other terms and definitions
18	3.3 Abbreviations and symbols
19	3.4 Conventions Figures Figure 1 – Common structure of specific fields
20	Tables Table 1 – Conventions used for AE state machine definitions
21	4 FAL syntax description 4.1 General 4.2 FAL-AR PDU abstract syntax
22	4.3 Abstract syntax of PDU body
23	4.4 Protocol data units (PDUs) for application service elements (ASEs) Table 2 – Status code for the confirmed response primitive
26	5 Transfer Syntax 5.1 Overview of encoding
27	5.2 APDU header encoding Figure 2 – APDU overview Figure 3 – Type field Table 3 – Encoding of FalArHeader field
28	5.3 APDU body encoding 5.4 Encoding of Data types Table 4 – Transfer Syntax for bit sequences
29	Table 5 – Transfer syntax for data type UNSIGNEDn
30	Table 6 – Transfer syntax for data type INTEGERn
31	Figure 4 – Encoding of Time of Day value
32	6 FAL protocol state machines Figure 5 – Encoding of Time Difference value
33	Figure 6 – Primitives exchanged between protocol machines
34	7 AP context state machine 8 FAL service protocol machine 8.1 General 8.2 Common parameters of the primitives 8.3 AP ASE protocol machine
35	Table 7 – Primitives exchanged between FAL-user and APAM
36	Figure 7 – State transition diagram of APAM Table 8 – Parameters used with primitives exchanged FAL-user and APAM Table 9 – APAM state table – Sender transitions
37	Table 10 – APAM state table – Receiver transitions Table 11 – Functions used by the APAM
38	8.4 Service data object ASE protocol machine (SDOM) Table 12 – Primitives exchanged between FAL-user and SDOM
39	Figure 8 – State transition diagram of SDOM Table 13 – Parameters used with primitives exchanged FAL-user and SDOM
40	Table 14 – SDOM state table – Sender transitions
41	Table 15 – SDOM state table – Receiver transitions Table 16 – Functions used by the SDOM
42	8.5 Process data object ASE protocol machine (PDOM) Figure 9 – State transition diagram of PDOM Table 17 – Primitives exchanged between FAL-user and PDOM Table 18 – Parameters used with primitives exchanged between FAL-user and PDOM
43	9 AR protocol machine 9.1 General Table 19 – PDOM state table – Sender transitions Table 20 – PDOM state table – Receiver transitions Table 21 – Functions used by the SDOM
44	9.2 Point-to-point user-triggered confirmed client/server AREP (PTC-AR) ARPM Table 22 – Primitives issued by user to PTC-ARPM Table 23 – Primitives issued by PTC-ARPM to user
45	Figure 10 – State transition diagram of PTC-ARPM Table 24 – PTC-ARPM state table – sender transactions
46	9.3 Multipoint network-scheduled unconfirmed publisher/subscriber AREP (MSU AR) ARPM Table 25 – PTC-ARPM state table – receiver transactions Table 26 – Function BuildFAL-PDU Table 27 – Primitives issued by user to ARPM Table 28 – Primitives issued by ARPM to user
48	Figure 11 – State transition diagram of MSU-ARPM Table 29 – MSU-ARPM state table – sender transactions Table 30 – MSU-ARPM state table – receiver transactions Table 31 – Function BuildFAL-PDU
49	9.4 Multipoint user-triggered unconfirmed publisher/subscriber AREP (MTU AR) ARPM Table 32 – Primitives issued by user to ARPM Table 33 – Primitives issued by ARPM to user
50	Figure 12 – State transition diagram of MTU-ARPM Table 34 – MTU-ARPM state table – sender transaction Table 35 – MTU-ARPM state table – receiver transactions
51	10 DLL mapping protocol machine 10.1 Primitive definitions Table 36 – Function BuildFAL-PDU Table 37 – Primitives issued by ARPM to DMPM Table 38 – Primitives issued by DMPM to ARPM Table 39 – Primitives issued by DMPM to DLL Table 40 – Primitives issued by DLL to DMPM
52	10.2 DMPM state machine Figure 13 – State transition diagram of DMPM Table 41 – DMPM state table – sender transactions Table 42 – DMPM state table – receiver transactions
53	Bibliography

Published By	Publication Date	Number of Pages
BSI	2012	56


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Status	Withdrawn
Title	Industrial communication networks. Fieldbus specifications – Application layer protocol specification. Type 21 elements
Replaces	DD IEC/PAS 62573:2008
Publisher	BSI
Committee	GEL/65/3
Pages	56
Publication Date	2012-07-31
Withdrawn Date	2022-07-29
Replaced By	BS EN IEC 61158-6-21:2019
ISBN	978 0 580 71572 3
Standard Number	BS EN 61158-6-21:2012
Identical National Standard Of	EN 61158-6-21:2012, IEC 61158-6-21:2010
Descriptors	Data processing, Computer networks, Process control, CSMA/CD networks, Data transmission, Industrial, Local area networks, Data transfer, Real-time systems, Data circuit-terminating equipment, Automatic control systems
ICS Codes	35.100.70 - Application layer

BS EN 61158-6-21:2012

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