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 26 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 behavior
provided by the Type 26 of the fieldbus Application Layer in terms of:
a) the abstract syntax defining the application layer protocol data units conveyed between
communicating application entities;
b) the transfer syntax defining the application layer protocol data units conveyed between
communicating application entities;
Open preview (PDF)Industrial communication networks. Fieldbus specifications - Application layer protocol specification. Type 26 elements
