Discrete Input (Di) Function Block Overview; Modes; Block Initialization; Status Handling - Emerson Fisher FIELDVUE DVC6000f Instruction Manual

TRANSDUCER
BLOCK
OUT_D = The block output and status
Figure 4-30. Discrete Input (DI) Function Block
Discrete Input (DI) Function Block
Overview
The Discrete Input (DI) function block processes a
single discrete input from a field device and makes it
available to other function blocks. You can configure
inversion and alarm detection on the input value. In
the DVC6000f digital valve controller, the discrete
input function block can provide limit switch
functionality and valve position proximity detection.
The DI function block supports mode control, signal
status propagation, and simulation.
Normally, the block is used in Automatic mode so that
the process variable (PV_D [7]) is copied to the output
(OUT_D [8]). You can change the mode to Manual to
disconnect the field signal and substitute a
manually-entered value for the output. In this case,
PV_D [7] continues to show the value that will become
the OUT_D [8] when the mode is changed to
Automatic.
To support testing, you can enable simulation, which
allows the measurement value to be supplied manually
through the SIMULATE_D [9] parameter. Figure 4-31
illustrates the internal components of the DI function
block, and table 4-80 lists the definitions of the block
parameters.

Modes

The Discrete Input function block supports the
following modes:
D Manual (Man)—The block output (OUT_D [8]) is
disconnected from the field and set manually.
D Automatic (Auto)—The block algorithm
determines output.
D Out of Service (OOS)—The block is not
processed. The OUT_D [8] status is set to Bad: Out of
December 2009
DI
OUT_D
DI Function Block
Service. The BLOCK_ERR [6] parameter shows Out
of Service.

Block Initialization

The Fieldbus Foundation specification requires that
certain parameters in the function blocks have initial
values of uninitialized. In addition to setting the
Resource block mode to AUTO, the control system or
the user must change those parameters from their
uninitialized value to a valid value in order for the
function block to move from the Out of Service mode.
For the DI function block, the CHANNEL [15]
parameter must be initialized.

Status Handling

Under normal conditions, a Good: Non-Cascade
status is passed through to OUT_D [8]. The block also
supports the Status Action On Failure and
BLOCK_ERR [6] indications.
When SIMULATE_D [9] is enabled, FIELD_VAL_D
[7], PV_D [7], and OUT_D [8] change to the simulated
status. When the block is set to Manual mode, OUT_D
[7] is set to Good: Non−cascade, Constant status.

I/O Selection

To select the I/O associated with the discrete
measurement, configure the value of the CHANNEL
[15] parameter.
In the digital valve controller, the four classes of
channels are
D Valve travel
D Open/Closed limit switch
D Variable limit switch based on transducer block
travel alarm settings.
D Proximity position detection based on transducer
block travel alarm settings.
The CHANNEL [15] parameter for each of the four DI
blocks available in the digital valve controller may be
set independently to achieve the desired position
detection. The DI block CHANNEL [15] definitions are
listed in table 4-76. Refer to the following descriptions
for details of the operation of these channels.
4
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