IEC 61158-4-21:2019 describes procedures for the timely transfer of data and control information from one data link user entity to a peer user entity, and among the data link entities forming the distributed data link service provider and procedures for giving communication opportunities based on standard ISO/IEC 8802-3 MAC, with provisions for nodes to be added or removed during normal operation; structure of the fieldbus data link protocol data units (DLPDUs) used for the transfer of data and control information by the protocol of this standard, and their representation as physical interface data units. This second edition cancels and replaces the first edition published in 2010. This edition constitutes a technical revision. The main changes are: •added Frame control Value, DLM function and DLL constants; •changed NCM_RETRY_RNMS to NCM_CHECK_NET_INTEGRITY_REQ; •updated DLM state table; •miscellaneous editorial corrections.

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PDF Pages	PDF Title
2	National foreword
5	Annex ZA(normative)Normative references to international publicationswith their corresponding European publications
7	CONTENTS
12	FOREWORD
14	INTRODUCTION
15	1 Scope 1.1 General 1.2 Specifications 1.3 Procedures 1.4 Applicability 1.5 Conformance
16	2 Normative references 3 Terms, definitions, symbols and abbreviations 3.1 Reference model terms and definitions
18	3.2 Service convention terms and definitions
19	3.3 Common terms and definitions
22	3.4 Additional Type 21 definitions 3.5 Common symbols and abbreviations
23	3.6 Additional Type 21 symbols and abbreviations
24	4 Overview of the data-link protocol 4.1 General 4.2 Overview of medium access control 4.3 Service assumed from the physical layer
25	4.4 DLL architecture 4.4.1 General Figures Figure 1 – Interaction of PhS primitives with DLE Tables Table 1 – DLL components
26	4.4.2 DLL management (DLM) interface support function Figure 2 – Data-link layer architecture
27	4.5 Data type 4.5.1 General 4.5.2 Boolean 4.5.3 Unsigned integer Table 2 – UNSIGNEDn data type
28	4.5.4 Signed integer 4.5.5 Octet String 4.5.6 Visible String Table 3 – INTEGERn data type
29	4.5.7 Time of day 4.6 Local parameters and variables 4.6.1 General 4.6.2 DLE configuration parameters
30	4.6.3 Queues to support data transfer Table 4 – DLE configuration parameters Table 5 – Queues to support data transfer
31	4.6.4 Variables to support SAP management Figure 3 – Relationships of DLSAPs, DLSAPaddresses, and group DLaddresses Table 6 – Variables to support SAP management
32	4.6.5 Variables to support local device information management Table 7 – Variables to support device information management
33	Table 8 – DL–entity identifier Table 9 – Device Flags Table 10 – DLM state
34	Table 11 – Device Unique Identification Table 12 – Unique identification of device connected to R-port1 Table 13 – Unique identification of device connected to R-port2 Table 14 – MAC address
35	Table 15 – Port information Table 16 – Protocol version
36	4.6.6 Variables and counter to support network information management Table 17 – Device type Table 18 – Device description Table 19 – Hop count
37	Table 20 – Variables to support managing network information Table 21 – Topology Table 22 – Collision count
38	Table 23 – Device count Table 24 – Topology change count Table 25 – Last topology change time Table 26 – RNMP device UID
39	Table 27 – RNMS device UID Table 28 – LNM device UID for R-port1 Table 29 – LNM device UID for R-port2
40	4.6.7 Variables and counter to support a device path information management Table 30 – Network flags
41	Table 31 – Variables and counter to support managing path information Table 32 – Hop count for R-port1 direction
42	Table 33 – Hop count for R-port2 direction Table 34 – Preferred R-port Table 35 – Destination R-port
43	Table 36 – In net count Table 37 – In net time
44	4.6.8 Variables, counters, timers, and queues to support path table management 5 General structure and encoding 5.1 Overview 5.2 MAPDU structure and encoding Table 38 – Out net count Table 39 – Out net time
45	5.3 Common MAC frame structure, encoding and elements of procedure 5.3.1 MAC frame structure 5.3.2 Elements of the MAC frame Figure 4 – Common MAC frame format for Type 21 DLPDU Figure 5 – MAC frame format for other protocols
46	5.3.3 Elements of the Type 21 DLPDU Figure 6 – Version and Length field
47	Figure 7 – DST_addr field Table 40 – Version and Length Table 41 – Destination DL–entity identifier
48	Figure 8 – SRC_addr field Figure 9 – Frame Control Field Table 42 – Source DL–entity identifier
49	Table 43 – Frame control
51	Figure 10 – Extension field
52	Figure 11 – DSAP field Table 44 – Extension Table 45 – Destination service access point
53	Figure 12 – Source service access point field Figure 13 – Length of group mask and extension information Figure 14 – Group mask option field Table 46 – source service access point
54	5.4 Order of bit transmission 5.5 Invalid DLPDU 6 DLPDU structure and procedure 6.1 General 6.2 Common DLPDU Field 6.2.1 General
55	6.2.2 Version 6.2.3 Length 6.3 DLDATA Transfer 6.3.1 DT DLPDU Figure 15 – Common DLPDU field Figure 16 – Building a DT DLPDU Figure 17 – DT DLPDU structure
56	Table 47 – DT DLPDU parameters
57	Table 48 – Primitives exchanged between DLSuser and DLE to send a DT DLPDU
58	6.4 DLSPDATA Transfer 6.4.1 SPDT DLPDU Figure 18 – SPDT DLPDU structure Table 49 – Primitives exchanged between DLSuser and DLEs to receive a DT DLPDU Table 50 – SPDT DLPDU Parameters
59	6.5 Network control messages 6.5.1 General 6.5.2 NCM_LA DLPDU Table 51 – Primitive exchanged between DLSUser and DLEs to send an SPDT DLPDU Table 52 – Primitives exchanged between DLSuser and DLEs to receive an SPDT DLPDU
60	Figure 19 – NCM_LA DLPDU structure Table 53 – NCM_LA DLPDU parameters
61	6.5.3 NCM_AT DLPDU Table 54 – NCM_AT DLPDU parameters
62	6.5.4 NCM_LS DLPDU Table 55 – NCM_LS DLPDU parameters
63	6.5.5 NCM_RS DLPDU Table 56 – NCM_RS DLPDU parameters
64	6.5.6 NCM_AR_DLPDU 6.5.7 NCM_AR DLPDU structure Table 57 – NCM_AR DLPDU parameters
65	7 DLE elements of procedure 7.1 Overall structure Figure 20 – DLL structure and elements
66	7.2 DLprotocol machine (DLPM) 7.2.1 Overview 7.2.2 Primitive definitions Table 58 – Primitives exchanged between DLPM and DLSuser
67	Table 59 – Parameters exchanged between DLPM and DLSuser
68	Table 60 – Primitives exchanged between DLPM and DLM
69	7.2.3 DLPM state table Figure 21 – State transition diagram of the DLPM Table 61 – Parameters used with primitives exchanged between DLPM and DLM
70	Table 62 – DLPM state table
73	7.2.4 DLPM functions Table 63 – DLPM functions table
74	7.3 DLL management Protocol 7.3.1 Overview 7.3.2 Primitive definitions
75	Table 64 – Primitives exchanged between DLM and DLSuser
76	Table 65 – Parameters used with primitives exchanged between DLM and DLSuser Table 66 – Primitive exchanged between DLM and DMAC
77	7.3.3 DLM state table Table 67 – Parameters used with primitives exchanged between DLM and DMAC Table 68 – Primitive exchanged between DLM and DPHY Table 69 – Parameters used with primitives exchanged between DLM and DPHY
78	Figure 22 – State transition diagram of DLM
79	Table 70 – DLM state table
101	7.3.4 DLM functions Table 71 – DLM function table
110	8 Constants and error codes 8.1 General
111	8.2 Constants Table 72 – DLL constants
112	8.3 Data-link layer error codes Table 73 – Type 21 DLL error codes
113	Bibliography

Published By	Publication Date	Number of Pages
BSI	2019	114


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Status	Withdrawn
Title	Industrial communication networks. Fieldbus specifications – Data-link layer protocol specification. Type 21 elements
Replaces	BS EN 61158-4-21:2012, BS EN 61158-4-21:2012
Publisher	BSI
Committee	GEL/65/3
Pages	114
Publication Date	2019-07-03
Withdrawn Date	2023-06-16
Replaced By	BS EN IEC 61158-4-21:2023
ISBN	978 0 539 04837 7
Standard Number	BS EN IEC 61158-4-21:2019
Identical National Standard Of	EN 61158-4-21:2019, IEC 61158-4-21:2019
Descriptors	Automatic control systems, Industrial, Process control, CSMA/CD networks, Data transfer, Real-time systems, Data transmission, Local area networks, Data circuit-terminating equipment, Data processing, Computer networks
ICS Codes	25.040.40 - Industrial process measurement and control

BS EN IEC 61158-4-21:2019

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BS EN IEC 61158-4-21:2019 – TC:2020 Edition