IEC 61158-1:2014 pdf download.Industrial communication networks - Fieldbus specifications
5 Concept of the IEC 61158 series
Conceptually, a fieldbus is an industrial digital communication network for integration of industrial control and instrumentation devices into a system. Examples of such devices are transducers, sensors, actuators and controllers.
The IEC 61158 series specifies a number of fieldbus protocol types. Each protocol type is designed to permit multiple measurement and control devices to communicate. Devices communicate directly only with other devices of the same protocol type. The basic requirements of industrial communication networks for measurement and control are given in Clause 11.
Devices which use the same lower-layer protocols in a compatible fashion but differ in their higher-layer protocols may be able to share a lower-layer medium.
In all cases, a particular data-link layer protocol type may be used without restriction when coupled with physical layer and application layer protocols of the same type or with other combinations as specified in IEC 61784-1 and IEC 61784-2. Use of the various protocol types in other combinations may require permission from their respective copyright holders.
The protocol types in IEC 61158 have been engineered to support information processing,monitoring and control systems for any industrial sector and related domains. An example application for high-integrity low-level communication between sensors, actuators and local controllers in a process plant, together with the interconnection of programmable controllers,is shown in Figure 1.
A number of fieldbus types are specified in the IEC 61158 series using the following concepts for decomposition.
a) First concept: The complex communication task is divided into different layers based on an adaptation of ISO/IEC 7498-1, the ISO/OSI Basic Reference Model, thereby facilitating well-structured functions and interfaces (see Clause 6). This has the following benefits:
- decomposition of complex tasks;
- modular structure to adapt different technologies.
b) Second concept: Each fieldbus type is composed of one or more layer specifications.
Most types include a number of services and protocol options that require an appropriate selection to support a working system. Compatible selections of options and services within one of the IEC 61158 fieldbus types are specified as standardized communication profiles in IEC 61784-1 and IEC 61784-2. Most of these profiles are supported by consortia or trade associations which are identified in the profile specification.
c) Third concept:
The physical, data-link and application layers are described in complementary ways, in terms of the offered services and the protocol which provides those services .
Figure 2 illustrates the differences between service and protocol viewpoints of the data-link and application layers. The protocol parts show the layer implementer's oriented view and the service parts show the layer user's oriented view.IEC 61158-1 pdf download.