50.02.6
ANSI/ISA-50.02, Part 6-1998 - Fieldbus Standard for Use in Industrial Control Systems Part 6: Application Layer Protocol Specification
General reference, softbound, 308pp.
$190.00

Describes the Fieldbus Application Layer (FAL) protocol that defines the information interchange and the interactions between Application Entity invocations (AE-Is) to support the services defined in ANSI/ISA-50.02, Part 5-1998, Fieldbus Standard for Use in Industrial Control Systems Part 5: Application Layer Service Definition. It specifies interactions between remote applications in terms of: encoding rules that are applied to all the Application Layer Protocol Data Units (APDUs); the formal Abstract Syntax definitions of such APDUs; the protocol state machine descriptions that handle the APDUs and the primitives in the correct sequences; and the mappings of the APDUs to and from the Data Link Layer services defined in ANSI/ISA-50.02, Part 3-1997, Fieldbus Standard for Use in Industrial Control Systems Part 3: Data Link Service Definition.

Scope:
The Fieldbus Application Layer (FAL) is an Application Layer communication standard designed to support the conveyance of time-critical application requests and responses among devices in an automation environment. The term ’time-critical’ is used to represent the presence of a time-window, within which one or more specified actions must be completed with some defined level of certainty. Failure to complete specified actions within the time window risks failure of the applications requesting the actions, with attendant risk to equipment, plant and possibly human life.

This document specifies interactions between remote applications in terms of:

• The encoding rules that are applied to all the Application Layer Protocol Data Units (APDUs).
  
• The formal Abstract Syntax definitions of such APDUs.
  
• The protocol state machine descriptions that handle the APDUs and the primitives in the correct sequences.
  
• The mappings of the APDUs to and from the Data Link Layer services defined in ISA-S50.02, Part 3-1997.

The FAL encoding rules are designed assuming that both the encoder (sender) and the decoder (receiver) have the common knowledge of the abstract syntax. Wherever possible, data types identifiers are not encoded and transferred over the network.

NOTE — This is why the Abstract Syntax Notation One / Basic Encoding Rule is not practical for the FAL.

The purpose of this document is to define the protocol provided to the Fieldbus Data Link Layer at the boundary between the Application and Data Link Layers of the Fieldbus Reference Model, and to the System Management at the boundary between the System Management and Application Layers of the Fieldbus Reference Model.

Purpose:

This document describes the Fieldbus Application Layer (FAL) protocol that defines the information interchange and the interactions between Application Entity invocations (AE-Is) to support the services defined in ISA-S50.02, Part 5-1998.

An Application Process uses the Fieldbus Application Layer services to exchange information with other Application Processes. The services define the abstract interface between the application process and the Application Layer.

The Application Layer protocol is the set of rules that governs the format and meaning of the information exchange between the Application Layers in various devices. The Application Layer uses the protocol to implement the Application Layer services definitions.

The protocol machine defines the various states of an Application Layer and the valid transitions between the states. It may be considered as a finite state machine. The protocol machine is described using state tables. The information is exchanged between the application process and the protocol machine through application service data units. The protocol machine exchanges information with other protocol machines through application protocol data units (APDU).

This set of Application Layer standards does not specify individual implementations or products, nor does it constrain the implementations of Application Entities (AEs) and interfaces within the industrial automation system.

This set of Application Layer standards does not contain test procedures to ensure compliance with such requirements.