Owner's manual

FOUNDATION
TM
Fieldbus Blocks Manual
8-4
Block Execution The ISEL function block reads the values and statuses of as many as
four inputs. To specify which of the six available methods (algorithms)
is used to select the output, configure the selector type parameter
(SEL_TYPE) as follows:
• max selects the maximum value of the inputs.
• min selects the minimum value of the inputs.
• avg calculates the average value of the inputs.
• mid calculates the middle of three inputs or the average of the
middle two inputs if four inputs are defined.
• 1st Good selects the first available good input.
• Hot Backup latches on the selected input and continues to use it
until it is bad.
If the DISABLE_N is active, the associated input is not used in the
selection algorithm.
If the OP_SELECT is set to a value between 1 and 4, the selection type
logic is overridden and the output value and status is set to the value
and status of the input selected by OP_SELECT.
SELECTED will have the number of the selected input unless the
SEL_TYPE is average, in which case it will have the number of inputs
used to calculate its value.
Status Handling In Auto mode, OUT reflects the value and status quality of the selected
input. If the number of inputs with Good status is less than
MIN_GOOD, the output status will be Bad.
In Man mode, the OUT status high and low limits are set to indicate
that the value is a constant and the OUT status is always Good.
In the STATUS_OPTS parameter, you can select from the following
options to control the status handling:
• Use Uncertain as Good: sets the OUT status quality to Good
when the selected input status is Uncertain.
• Uncertain if in Manual mode: The status of the Output is set
to Uncertain when the mode is set to manual.
NOTE
The instrument must be in Manual or Out of Service mode to set the
status option.