DIN EN 61158-4-7-2008 工业通讯网络.现场总线规范.第4-7部分:数据联络层协议规范.7型元件.仅为CD-ROM
Industrial communication networks - Fieldbus specifications - Part 4-7: Data-link layer protocol specification - Type 7 elements (IEC 61158-4-7:2007); English version EN 61158-4-7:2008, only on CD-ROM
1.1 General
The data-link layer provides basic time-critical messaging communications between devices in an
automation environment.
This protocol provides communication opportunities to all participating data-link entities
a) in a synchronously-starting cyclic manner, according to a pre-established schedule, and
b) in a cyclic or acyclic asynchronous manner, as requested each cycle by each of those data-link
entities.
Thus this protocol can be characterized as one which provides cyclic and acyclic access
asynchronously but with a synchronous restart of each cycle.
1.2 Specifications
This standard specifies
a) 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;
b) the structure of the fieldbus 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
a) the interactions between peer DL-entities (DLEs) through the exchange of fieldbus DLPDUs;
b) the interactions between a DL-service (DLS) provider and a DLS-user in the same system
through the exchange of DLS primitives;
c) the interactions between a DLS-provider and a Ph-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 which support
time-critical communications services within the data-link layer of the OSI or fieldbus reference
models, and which 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-critical communications needs.
1.5 Conformance
This standard also specifies conformance requirements for systems implementing these procedures.
This part of this standard does not contain tests to demonstrate compliance with such requirements.