IEC/PAS 63693 Ed. 1.0 en:2026

IEC PAS 63693:2026 provides the common elements for basic time-critical messaging communications between devices in an automation environment and user programs with a means to access the fieldbus communication environment.

The term time-critical is used to represent the presence of a time-window, within which one or more specified actions are required to 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 defines in an abstract way:

• a) The externally visible services provided by the WiTSnet in terms of:
  • 1) an abstract model for defining application resources (objects) capable of being manipulated by users via the use of the FAL services;
  • 2) the primitive actions and events of the services;
  • 3) the parameters associated with each primitive action and event, and the form which they take;
  • 4) the interrelationship between these actions and events, and their valid sequences.
• b) The externally visible behavior provided by the WiTSnet in terms of:
  • 1) the abstract syntax defining the data-link layer and application layer protocol data units conveyed between communicating data-link and application entities;
  • 2) the transfer syntax defining encoding rules that are applied to the data-link layer and the application layer protocol data units;
  • 3) the data-link and the application context state machines defining the data-link and the application service behaviors visible between communicating data-link and application entities; and
  • 4) the data-link and the application relationship state machines defining the data-link and the application service behaviors visible between communicating data-link and application entities.

The purpose of this document is to define the services provided to:

• c) the WiTSnet fieldbus application layer at the boundary between the application and data-link layers of the Fieldbus Reference Model;
• d) systems management at the boundary between the data-link layer and systems management of the Fieldbus Reference Model;
• e) the FAL user at the boundary between the user and the application layer of the Fieldbus Reference Model; and
• f) systems management at the boundary between the application layer and systems management of the Fieldbus Reference Model.

The purpose of this document is to define the protocol provided to:

• g) define the wire-representation of the service primitives defined in clause 7; and
• h) define the externally visible behavior associated with their transfer.