Status Handling; Setting The Output - Emerson Fisher FIELDVUE DVC6000f Instruction Manual

Operator
Setpoint
CAS IN
B2717 / IL
Auto—On failure of a remote cascade connection, the
block sets the target mode to Auto, if permitted.
Man—On failure of remote cascade connection, the
block sets the target mode to Man, if permitted.
The user may configure SHED_OPT [27] so that it
calls for a target mode that is not permitted. When
doing this, the mode logic uses the following rules as
applied by the remote logic:
D Shed logic never results in a non-permitted target
mode.
D Shed logic never attempts to attain an actual
mode of Auto or Cas if that mode is not permitted.

Status Handling

Output or readback fault detection is reflected in the
status of PV [7], OUT [9], and BKCAL_OUT [25]. A
limited SP [8] condition is reflected in the
BKCAL_OUT [25] status. When simulation is enabled
through the SIMULATE [10] attribute, you can set the
value and status for PV [7] and READBACK [16].
December 2009
RCAS
RCAS IN
SP RATE DN
SP RATE UP
SP SP
HI/LO Rate
Limit Limit
SP WRK
SP LOW LIM
SP HI LIM
MODE
Shed
Mode
Access
Analog
Input
Position
Feedback
Figure 4-9. Analog Output Function Block Schematic
AO Function Block
OUT
READ BACK
PV
Convert
and Status
Calculation
PV SCALE
IO OPTS
Access
Analog
CHANNEL
Output
Analog
Output
When the block is in Cas mode and the CAS_IN [17]
input goes bad, the block sheds mode to the next
permitted mode.

Setting the Output

To set the output for the AO block, you must first set
the mode to define the manner in which the block
determines its setpoint. In Manual mode the value of
the output attribute (OUT [9]) must be set manually by
the user, and is independent of the setpoint. In
Automatic mode, OUT [9] is set automatically based
on the value specified by the set point (SP [8]) in
engineering units and the I/O Options attribute. In
addition, you can limit the SP [8] value and the rate at
which a change in the SP [8] is passed to OUT [9].
In Cascade mode, the cascade input connection
(CAS_IN [17]) is used to update the SP [8]. The back
calculation output (BKCAL_OUT [25]) is wired to the
back calculation input (BKCAL_IN [27]) of the
upstream block that provides CAS_IN [17]. This
provides bumpless transfer on mode changes and
windup protection in the upstream block.
BKCAL OUT
OUT
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