Emerson DXP-FF, Инструкция по установке, эксплуатации и обслуживанию

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Appendix D: Discrete Output (DO)
Discrete OUTPUT Blocks (DO Block)
There are 3 F
OUNDATION
Fieldbus standard DO blocks and 5 output channels.
The DO blocks take discrete control data and translate it to actuation in the field.
These blocks are used to open and close the valve. There are 4 different strate-
gies provided to open and close a valve, depending on the system being used,
and whether a single or dual action pilot valve is being used.
Single Block Control Method, Single Action (Default)
Set the Channel Parameter of DO1 to 1(Open/Close Output), and DO2 and DO3
to 0 (No Connection). The valve is now controlled by the wiring going to the V1
terminals. By writing a 0 or a 1 to this DO block will now open and close the
valve.
Single Block Control Method, Dual Action
Set the Channel Parameter of DO1 to 5 (Open/Close/Stop Output), and DO2
and DO3 to 0. The valve is now controlled by the wiring going to the V1 termi-
nals and V2 terminals. By writing a 0 or a 1 to this DO block will now open and
close the valve. Writing a 2 to the DO block will de-energize both the V1 and V2
terminals, stopping a valve using a block center type of pneumatic valve.
Dual Block Control Method, Single Action
Set the Channel Parameter of DO1 to 2 (Open), DO2 to 3 (Close), and DO3 to
0. Now by writing a 1 to DO1, the valve will Open. Changing this value back to
0, and writing a 1 to DO2 will cause the valve to close.
Three Block Control Method, Dual Action
Set the Channel Parameter of DO1 to 2 (Open) , DO2 to 3 (Close), and DO3 to
4 (Stop). Now by writing a 1 to DO1, the valve will Open. Changing this value
back to 0, and writing a 1 to DO2 will cause the valve to close. Changing this
value back to 0, and writing a 1 to DO3 will cause the outputs to terminals V1
and V2 to turn off, stopping an actuator using a block center pneumatic valve.
Note on Energize to Close
To energize to close (also called Reverse Acting), the ACTION_ELEMENT
parameter must be reset to Reverse Acting. See the Transducer section for
more details.
To use the READBACK_D values for the BACK CALCULATION OUTPUT
DISCRETE parameter of the DO block, the following two options must be selected:
1. In the Resource Block the “Output Readback” option should be selected.
2. In the DO Block under IO_OPTS, select the “Use PV for BKCAL_OUT” option.
Configuration Error Handling
In order to minimize configuration errors, several write checking features have
been added to the SCM-FF. Write checks to the CHANNEL parameter of the DO
blocks should prevent illegal configurations. These illegal configurations are:
1. If the two-state
Channel 1 Open-Close
has been assigned, an attempt to
assign Channel 2 Open, Channel 3 Close or the Channel 5 Open/Close/
Stop channels will be rejected with a write check.
2. If the three-state
Channel 5 Open-Close-Stop
has been assigned, an
attempt to assign the Channel 2 Open, the Channel 3 Close or the Chan-
nel 1 Open/Close channels will be rejected with a write check.
3. If the channel you are trying to assign has already been assigned to an-
other Function Block, the write will be rejected with a write check.
4. If the Open channel has been assigned and the Close channel has not,
an ‘Open without Close’ block alarm is generated by the block. NO OTH-
ER LOCK-OUTS ARE IMPLEMENTED (no write-check). This
becomes an open only valve. Without the close signal, the last position
will be maintained.
5. If the Close channel has been assigned and the Open channel has not,
a ‘Conflicting Channels Assigned’ block alarm is generated by the block.
NO OTHER LOCK-OUTS ARE IMPLEMENTED (no write-check).
This becomes a close only valve.
Error handling for the configuration of channels has been modified as well. The
Transducer Block has a special BLOCK_ALARMS_ACTIVE parameter which may
be used to diagnose a configuration problem. The configuration errors are listed in
Table 2.
Table 1. Discrete Output Channel Assignments
Table 2. Transducer Block’s
BLOCK_ALARMS_ACTIVE Parameter