Glossary
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National Instruments Corporation
G-3
NI-FBUS Hardware and Software User Manual
Connection Management
The service the NI-FBUS Communications Manager provides by
handling Virtual Communication Relationships.
Control loop
A set of connections between blocks used to perform a control
algorithm.
Controller
An intelligent device (usually involving a CPU) that is capable of
controlling other devices.
ControlNet
A 5 Mbit/s communications protocol based on Producer/Consumer
technology.
Core Function
The basic functions that the NI-FBUS Communications Manager
software performs, such as reading and writing block parameters.
D
Data Link Layer
The second-lowest layer in the ISO seven-layer model (layer two).
The Data Link Layer splits data into frames to send on the physical
layer, receives acknowledgment frames, and re-transmits frames if
they are not received correctly. It also performs error checking to
maintain a sound virtual channel to the next layer.
DD
See
Descriptor
A number returned to the application by the NI-FBUS
Communications Manager, used to specify a target for future
NI-FBUS calls.
Device
A sensor, actuator, or control equipment attached to the Fieldbus.
Device Description
A machine-readable description of all the blocks and block
parameters of a device.
Device Description
Language
A formal programming language that defines the parameters of the
blocks. It also defines attributes of parameters and blocks like help
strings in different languages, ranges of values for parameters,
and so on.
Device Description
Service
A set of functions that applications use to access Device Descriptions.
Device tag
A name you assign to a Fieldbus device.
Directory
A structure for organizing files into convenient groups. A directory
is like an address showing where files are located. A directory can
contain files or subdirectories of files.