Rockwell Automation 1757-FFLDC4 FOUNDATION Fieldbus System User Manual - Manual (Page 177)

Rockwell Automation Publication 1757-UM012A-EN-P - July 2011 177
Glossary
tag ID Unique alphanumeric code assigned to inputs, outputs, equipment items, and
control blocks.
terminator Impedance-matching module used at or near each end of a transmission line
that has the same characteristic impedance of the line. Terminators are used to
minimize signal distortion, which can cause data errors. H1 terminators
convert the current signal transmitted by one device to a voltage signal that can
be received by all devices on the network.
transducer block The transducer block decouples function blocks from the local
input/output (I/O) function required to read sensors and command output
hardware. Transducer blocks contain information, such as calibration date and
sensor type. There is usually one transducer block for each input or output of a
function block.
USB A Universal Serial Bus (USB) establishes communication between a device and
a host controller.
user layer Provides scheduling of function blocks as well as device descriptions that let
the host system communicate with devices without the need for custom
programming.
VCR Acronym for Virtual Communication Relationship. Configured application
layer channels that provide for the transfer of data between applications.
FOUNDATION Fieldbus describes three types of VCRs: Publisher/Subscriber,
Client/Server, and Source/Sink.