Discrete Output (Do) Function Block; Shed Options — Rcas Mode Only - Emerson Fisher Fieldvue DVC6030f Instruction Manual

DVC6000f Series
CAS_IN_D
CAS IN D = The remote set point value from
another function block.
BKCAL OUT D = The value and status required by the
BKCAL IN D input of another block for
output tracking.
OUT_D = The block output and status.
READBACK_D = Actual valve position
Figure 5-28. Discrete Output (DO) Function Block
5

Discrete Output (DO) Function Block

Overview
The Discrete Output (DO) function block processes a
discrete set point and outputs it to the specified I/O
channel to produce an output signal. The DVC6000f
Series digital valve controller discrete output block
provides both normal open/closed control and the
ability to position the valve in 5% increments for
coarse throttling applications. The digital valve
controller measures and uses actual valve position for
READBACK_D [16].
The DO block supports mode control and simulation.
In operation, the DO function block determines its set
point and sets the output. The transducer block
provides a readback signal of actual position from the
instrument. Figure 5-28 illustrates the primary inputs
and outputs of the DO function block, figure 5-29
illustrates the internal components of the DO function
block. Table 5-71 lists definitions for the function block
parameters.
When setting up the DO block, CHANNEL [18] must
be set to 22, and SHED_OPT [23] must be non-zero.
Note
Feature Select in the resource block
must have the DO Control option set
for the DO block to be fully functional.
5-146
BKCAL_OUT_D
DO
OUT_D
READBACK_D
Modes
The DO block supports the following modes:
D Manual (Man)—The block output OUT_D [9]
value may be entered manually.
D Automatic (Auto)—The block algorithm uses
the local set point SP_D [8]value to determine OUT_D
[9].
D Cascade (Cas)—The block uses a set point
supplied by another function block.
Note
The transducer block must be in Auto
for the mode to go to AUTO, CAS or
MAN.
D RemoteCascade (RCas)—The block uses a set
point supplied by a host computer.
D Out of Service (OOS)—The block is not
processed and the output is not transferred to I/O. The
BLOCK_ERR [6] attribute shows Out of service.
Mode Handling
Shed Options — RCAS Mode Only
Shed from or climb to a remote mode is determined by
the parameter SHED_OPT [23]. A block climbs and
sheds through the same path. For example, if
SHED_OPT [23] specifies that a block should shed to
Auto, then, if the block target mode is set to RCas, the
block goes through Auto on the way to RCas. You can
configure the shed option as follows:
Shed With Return Options
Remote cascade connection failure shifts actual mode
but keeps trying to restore remote cascade (in other
words, the remote cascade target mode stays in
effect).
Normal—On failure of a remote cascade connection,
the block attempts to attain the highest permitted
non-remote mode until remote cascade is restored.
Cas is the highest permitted non-remote mode and
Auto is is the next permitted non-remote mode. If Cas
or Auto are not available, the block will shed by default
to Man.
March 2006