ISA 50.02-4 : 1997

Introduction
    Keywords
    General
    Purpose
    Intended Users
1 Scope
    1.1 Specifications
    1.2 Procedures
    1.3 Applicability
    1.4 Conformance
2 Normative references
3 Definitions
    3.1 Reference model definitions
    3.2 Service convention definitions
    3.3 Data Link Service definitions
4 Symbols and abbreviations
    4.1 Data units
    4.2 Local variables, timers, counters and queues
    4.3 DLPDU classes
    4.4 Miscellaneous
5 Overview of the DL-protocol
    5.1 Three-level model of the DLL
    5.2 Service provided by the DLL
    5.3 DL-addresses
    5.4 Service assumed from the Physical Layer
    5.5 Functions of the DLL
    5.6 Functional classes
    5.7 Local parameters, variables, counters, timers
          and queues
6 General structure and encoding of PhIDUs and DLPDUs,
    and related elements of procedure
    6.1 PhIDU structure and encoding
    6.2 Common DLPDU structure, encoding and elements
          of procedure
7 DLPDU-specific structure, encoding and elements of
    procedure
    7.1 Establish Connection (EC) DLPDU
    7.2 Disconnect Connection (DC) DLPDU
    7.3 Reset Connection (RC) DLPDU
    7.4 Compel Acknowledgement (CA) DLPDU
    7.5 Compel Data (CD) DLPDU
    7.6 Exchange Data (ED) DLPDU
    7.7 Data (DT) DLPDU
    7.8 Status Response (SR) DLPDU
    7.9 Compel Time (CT) DLPDU
    7.10 Time Distribution (TD) DLPDU
    7.11 Round-Trip-Delay Query (RQ) DLPDU
    7.12 Round-Trip-Delay Reply (RR) DLPDU
    7.13 Probe Node DL-address (PN) DLPDU
    7.14 Probe Response (PR) DLPDU
    7.15 Pass Token (PT) DLPDU
    7.16 Execute sequence (ES) DLPDU
    7.17 Return Token (RT) DLPDU
    7.18 Request Interval (RI) DLPDU
    7.19 Claim LAS (CL) DLPDU
    7.20 Transfer LAS (TL) DLPDU
    7.21 Wakeup (WK) DLPDU
    7.22 Idle (IDLE) DLPDU
    7.23 Spare DLPDUs
    7.24 Reserved (Can't use) DLPDUs
8 DLPDU-parameter structure and encoding
    8.1 Structure and encoding of EC-Parameters
    8.2 Structure and encoding of DC-Parameters
    8.3 Structure and encoding of RC-Parameters
    8.4 Structure and encoding of SD-Parameters
    8.5 Structure and encoding of SR-Parameters
    8.6 Structure and encoding of TD-Parameters
    8.7 Structure and encoding of RQ-Parameters
    8.8 Structure and encoding of RR-Parameters
    8.9 Structure and encoding of PN-Parameters
    8.10 Structure and encoding pf DD-Parameters
9 DL-service elements of procedure
    9.1 Operation of the DL(SAP)-address, buffer and
          queue management services
    9.2 Operation of the connection-mode services
    9.3 Operation of the connectionless-mode services
    9.4 Operation of the scheduling guidance services
10 Other DLE elements of procedure
    10.1 DLE initialization
    10.2 LAS behavior and operation
    10.3 DL-support operation
11 Implementation profiles
    11.1 DL-address, queue and buffer management
          services
    11.2 DL-data delivery services
    11.3 DL-time and time-based scheduling services
Annexes
      A - (normative) Structure and definition of
           DL-addresses
      B - (normative) DL-support sub-protocol
      C - (normative) DL-bridge elements of procedure
           and bridge
      D - (normative) DL-management-information
      E4 - (normative) PICS proforma
      F - (informative) Formal protocol finite state
           machines
      G - (informative) Exemplary FCS implementation
      H - (informative) DLPDU and DL-addressing
           short-form summaries
Figures
Tables

Designed to support time-critical messaging communications to and from devices in an automation environment. Defines methods for a single protocol for transferring data and controlling information from one data-link user entity to a peer user entity, and among data-link entities forming the distributed data-link service provider, and the structure of the Fieldbus Data Link (DL) Protocol Data Units used for transferring data and controlling information, and their representation as Physical Interface Data Units.