1.1 General

The DLL provides basic time-critical data communications between devices in an automated environment. Type 21 provides priority-based cyclic and acyclic data communication using an internal collision-free, full-duplex dual-port Ethernet switch technology. For wide application in various automation applications, Type 21 does not restrict the cyclic/acyclic scheduling policy in the DLL.

1.2 Specifications

This standard 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;
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.

1.3 Procedures

The procedures are defined in terms of:

the interactions between peer data link entities (DLEs) through the exchange of fieldbus DLPDUs;
the interactions between a data link service (DLS) provider and a DLS-user in the same system through the exchange of DLS primitives;
the interactions between a DLS-provider and a physical layer service provider in the same system through the exchange of Ph-service primitives.

1.4 Applicability

These procedures are applicable to instances of communication between systems that support time-critical communications services in the data link layer of the OSI or fieldbus reference models, and that require the ability to interconnect in an open systems interconnection environment. Profiles provide a simple multi-attribute means of summarizing an implementation’s capabilities, and thus its applicability to various time-deterministic communications needs.

1.5 Conformance

This standard also specifies conformance requirements for systems implementing these procedures. This standard does not contain tests to demonstrate compliance with such requirements.

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PDF Pages	PDF Title
6	CONTENTS
10	INTRODUCTION
12	1 Scope 1.1 General 1.2 Specifications 1.3 Procedures 1.4 Applicability
13	1.5 Conformance 2 Normative references 3 Terms, definitions, symbols and abbreviations 3.1 Reference model terms and definitions
15	3.2 Service convention terms and definitions
16	3.3 Common terms and definitions
17	Figures Figure 1 – Relationships of DLSAPs, DLSAP addresses, and group DL addresses
19	3.4 Symbols and abbreviations
20	4 Overview of the data-link protocol 4.1 General 4.2 Overview of medium access control
21	4.3 Service assumed from the physical layer 4.4 DLL architecture Figure 2 – Interaction of PhS primitives with DLE
22	Figure 3 – Data-link layer architecture Tables Table 1 – DLL components
23	4.5 Data type
24	Table 2 – UNSIGNEDn data type
25	4.6 Local parameters and variables Table 3 – INTEGERn data type
26	Table 4 – DLE configuration parameters
27	Table 5 – Queues to support data transfer
28	Table 6 – Variables to support SAP management Table 7 – Variables to support device information management
29	Table 8 – DL–entity identifier Table 9 – Device Flags Table 10 – DLM state
30	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
31	Table 15 – Port information Table 16 – Protocol version
32	Table 17 – Device type Table 18 – Device description Table 19 – Hop count
33	Table 20 – Variables to support managing network information Table 21 – Topology Table 22 – Collision count
34	Table 23 – Device count Table 24 – Topology change count Table 25 – Last topology change time Table 26 – RNMP device UID
35	Table 27 – RNMS device UID Table 28 – LNM device UID for R-port1 Table 29 – LNM device UID for R-port2
36	Table 30 – Network flags
37	Table 31 – Variables and counter to support managing path information
38	Table 32 – Hop count for R-port1 direction Table 33 – Hop count for R-port2 direction Table 34 – Preferred R-port Table 35 – Destination R-port
39	Table 36 – In net count Table 37 – In net time
40	5 General structure and encoding 5.1 Overview 5.2 MAPDU structure and encoding Table 38 – Out net count Table 39 – Out net time
41	5.3 Common MAC frame structure, encoding and elements of procedure Figure 4 – Common MAC frame format for Type 21 DLPDU Figure 5 – MAC frame format for other protocols
42	Figure 6 – Version and Length field
43	Figure 7 – DST_addr field Table 40 – Version and Length Table 41 – Destination DL–entity identifier
44	Figure 8 – SRC_addr field Table 42 – Source DL–entity identifier
45	Figure 9 – Frame Control Field Table 43 – Frame control
47	Figure 10 – Extension field Table 44 – Extension
48	Figure 11 – DSAP field Figure 12 – Source service access point field Table 45 – Destination service access point Table 46 – source service access point
49	5.4 Order of bit transmission 5.5 Invalid DLPDU Figure 13 – Length of group mask and extension information Figure 14 – Group mask option field
50	6 DLPDU structure and procedure 6.1 General 6.2 Common DLPDU Field 6.3 DL DATA Transfer Figure 15 – Common DLPDU field
51	Figure 16 – Building a DT DLPDU Figure 17 – DT DLPDU structure Table 47 – DT DLPDU parameters
53	6.4 DL SPDATA Transfer Table 48 – Primitives exchanged between DLS user and DLE to send a DT DLPDU Table 49 – Primitives exchanged between DLS user and DLEs to receive a DT DLPDU
54	Figure 18 – SPDT DLPDU structure Table 50 – SPDT DLPDU Parameters
55	6.5 Network control messages Table 51 – Primitive exchanged between DLS User and DLEs to send an SPDT DLPDU Table 52 – Primitives exchanged between DLS user and DLEs to receive an SPDT DLPDU
56	Figure 19 – NCM_LA DLPDU structure Table 53 – NCM_LA DLPDU parameters
57	Table 54 – NCM_AT DLPDU parameters
58	Table 55 – NCM_LS DLPDU parameters
59	Table 56 – NCM_RS DLPDU parameters
60	Table 57 – NCM_AR DLPDU parameters
61	7 DLE elements of procedure 7.1 Overall structure 7.2 DL protocol machine (DLPM) Figure 20 – DLL structure and elements
62	Table 58 – Primitives exchanged between DLPM and DLS user
63	Table 59 – Parameters exchanged between DLPM and DLS user
64	Table 60 – Primitives exchanged between DLPM and DLM
65	Figure 21 – State transition diagram of the DLPM Table 61 – Parameters used with primitives exchanged between DLPM and DLM
66	Table 62 – DLPM state table
70	Table 63 – DLPM functions table
71	7.3 DLL management Protocol
72	Table 64 – Primitives exchanged between DLM and DLS user
73	Table 65 – Parameters used with primitives exchanged between DLM and DLS user Table 66 – Primitive exchanged between DLM and DMAC
74	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
75	Figure 22 – State transition diagram of DLM
77	Table 70 – DLM state table
102	Table 71 – DLM function table
104	8 Constants and error codes 8.1 General 8.2 Constants
105	Table 72 – DLL constants
106	8.3 Data-link layer error codes Table 73 – Type 21 DLL error codes
107	Bibliography

Published By	Publication Date	Number of Pages
BSI	2013	110


PDF Format	Searchable	Printable	Preview Now

Pages	110
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
Identical National Standard Of	IEC 61158-4-21:2010, EN 61158-4-21:2012
Standard Number	BS EN 61158-4-21:2012
ISBN	978 0 580 79704 0
Replaced By	BS EN IEC 61158-4-21:2019
Withdrawn Date	2022-07-29
Publication Date	2013-07-31
Committee	GEL/65/3
Publisher	BSI
Replaces	DD IEC/PAS 62573:2008
Corrects	BS EN 61158-4-21:2012
Title	Industrial communication networks. Fieldbus specifications – Data-link layer protocol specification. Type 21 elements
Status	Withdrawn
ICS Codes	25.040.40 - Industrial process measurement and control

BS EN 61158-4-21:2012:2013 Edition

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