50.02.5
ANSI/ISA-50.02, Part 5-1998 - Fieldbus Standard for Use in Industrial Control Systems Part 5: Application Layer Service Definition
General reference, softbound, 234pp.
$165.00

Describes the structure and services of the Fieldbus Application Layer (FAL). It specifies interactions between remote applications in terms of: an abstract model for defining application resources (objects) capable of being manipulated by users via the user of FAL Services; the primitives (interactions between the FAL and the FAL user) associated with each FAL Service; the parameters associated with each primitive; and the interrelationship between, and the valid sequences of, the primitives for each service.

Scope:
The Fieldbus Application Layer (FAL) provides user programs with a means to access the Fieldbus communication environment. In this respect, the FAL can be viewed as a window between corresponding application programs.

The FAL is an Application Layer Communication Standard designed to support the conveyance of time-critical and non-time-critical application requests and responses among devices in an automation environment. The term ’time-critical’ is used to represent the presence of an application time-window, within which one or more specified actions are required to be completed with some defined level of certainty.

This document specifies the structure and services of the Fieldbus Application Layer (FAL). It is specified in conformance with the OSI Basic Reference Model (ISO 7498) and the OSI Application Layer Structure (ISO 9545).

FAL services and protocols are provided by FAL application-entities (AE) contained within the application processes. The FAL AE is composed of a set of object-oriented Application Service Elements (ASEs) and a Layer Management Entity (LME) that manages the AE. The ASEs provide communication services that operate on a set of related application process object (APO) classes. One of the FAL ASEs is a management ASE that provides a common set of services for the management of the instances of FAL classes.

This document specifies interactions between remote applications in terms of:

• An abstract model for defining application resources (objects) capable of being manipulated by users via the use of FAL Services;
• The primitives (interactions between the FAL and the FAL user) associated with each FAL Service;
• The parameters associated with each primitive;
• The interrelationship between and the valid sequences of the primitives for each service.

Although these services specify, from the perspective of applications, how requests and responses are issued and delivered, they do not include a specification of what the requesting and responding applications are to do with them. That is, the behavioral aspects of the applications are not specified; only a definition of what requests and responses they can send/receive is specified. This permits greater flexibility to the FAL users in standardizing such object behavior. In addition to these services, some supporting services are also defined in this specification to provide access to the FAL to control certain aspects of its operation.

Purpose:
This document describes the Fieldbus Application Layer services intended to support the information interchange and the interactions between application processes.

This set of application layer standards does not specify individual implementations or products, nor does it constrain the implementations of Application entities and interfaces within the industrial automation system.

This set of application layer standards does not contain test specifications used to demonstrate compliance.