National Instruments FieldPoint FP-3000, User Manual

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Chapter 4 Block Reference
© National Instruments Corporation 4-9 FieldPoint FP-3000 User Manual
over the Fieldbus using a host configuration tool, the block that is sending
data to the other block is called the publisher. The block receiving the data
is called the subscriber. When communication is established from a
publisher to a subscriber, the subscriber takes on the value and the status of
the published variable. If communication is not established between the
publisher and the subscriber, the subscriber has a status that reflects the lack
of communication. Statuses themselves are composed of three subfields:
the quality, the substatus, and the limit.
Quality
Table 4-3 describes the
Quality
subfields.
Substatus
The
Substatus
field is used to describe more specifically the cause of the
given quality. For example, a status with the quality of
Bad
might have a
substatus of
Device Failure
, indicating that the value should not be
trusted because it is from a device that has failed. Another common
substatus is
Non-specific
. The
Non-specific
substatus is used when
no other substatus applies. There are too many substatuses to explicitly list.
Table 4-3. Quality Values
Value Meaning
Bad
The value is bad, the sensor is defective, or
communication has not been established. The
value should not be trusted by the receiver.
Uncertain
The quality of the data is unknown. This can be
caused by errors or a lack of calibration in the
physical I/O transducer. Blocks can generally be
configured to treat values of
Uncertain
quality
as either
Bad
or
Good
with the
STATUS_OPTS
parameter.
Good_NonCascade
The value is good and from a block that does not
support cascade initialization. This status is also
used when an alarm is active.
Good_Cascade
The value is good and from a block that supports
cascade initialization.