1 Scope
1.1 General
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.”
This part of IEC 61158 provides common elements for basic time-critical and non-time-critical messaging
communications between application programs in an automation environment and material
specific to Type 19 fieldbus. 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 International Standard defines in an abstract way the externally visible service
provided by the different Types of fieldbus Application Layer in terms of:
a) an abstract model for defining application resources (objects) capable of being manipulated
by users via the use of the FAL service;
b) the primitive actions and events of the service;
c) the parameters associated with eac...