Справочник Пользователя для National Instruments FP-3000
Chapter 4
Block Reference
4-8
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National Instruments Corporation
TIME_STAMP
The time the alarm was detected by the FP-3000. In FOUNDATION
Fieldbus, all devices share a common sense of time. This shared sense of
time is used to timestamp alarm conditions as they occur, rather than when
they are reported.
Fieldbus, all devices share a common sense of time. This shared sense of
time is used to timestamp alarm conditions as they occur, rather than when
they are reported.
SUBCODE
For Block alarm, the subcode of the last error condition detected. The
Block alarm, shared by all FOUNDATION Fieldbus function blocks in the
FP-3000, is unique in that there are multiple conditions that can cause it to
go active and clear. Any error condition reported in the
Block alarm, shared by all FOUNDATION Fieldbus function blocks in the
FP-3000, is unique in that there are multiple conditions that can cause it to
go active and clear. Any error condition reported in the
BLOCK_ERR
parameter of the block causes the block alarm to go active. The alarm does
not clear until the last error condition in
not clear until the last error condition in
BLOCK_ERR
has been resolved. To
indicate which error condition the
BLOCK_ALM
is reporting, the
SUBCODE
subfield of the parameter is set to indicate the block error condition causing
the fault. If additional error conditions are detected, the
the fault. If additional error conditions are detected, the
SUBCODE
and
TIME_STAMP
are updated to reflect the latest condition detected, but the
alarm will not be reported a second time until every error condition has
been resolved.
been resolved.
VALUE
For limit alarms, the value of the parameter causing the alarm condition
(the Process Variable). For update events, the index of the modified static
parameter.
(the Process Variable). For update events, the index of the modified static
parameter.
Status and Mode Handling Overview
Status and mode handling are crucial aspects of developing a distributed
control application. Mode refers to the mode of operation of a function
block; allowable modes depend on the type of block, but generally include
Out of Service mode, Manual mode, and Auto mode.
control application. Mode refers to the mode of operation of a function
block; allowable modes depend on the type of block, but generally include
Out of Service mode, Manual mode, and Auto mode.
Status refers to the quality of a variable communicated between two blocks.
When a block receives a variable with bad status, it can affect its current
mode of operation.
When a block receives a variable with bad status, it can affect its current
mode of operation.
Status Handling
Parameters that can be communicated between blocks are composed of a
value and a status. The value is the data to be communicated, and the status
describes the quality of the data. When two blocks are logically connected
value and a status. The value is the data to be communicated, and the status
describes the quality of the data. When two blocks are logically connected