BS EN 61158-5-4:2014 PDF

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 standard 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 4 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 standard defines in an abstract way the externally visible service provided by the Type 4 fieldbus application layer in terms of

a) an abstract model for defining applicationresources ( objects ) capable of being manipulated by users via the use of the FALservice,

b) the primitive actions and events of the