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Appendix C
Fieldbus Parameters
C-14
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National Instruments Corporation
NV_CYCLE_T
The time interval in milliseconds in which nonvolatile parameters are
committed to nonvolatile storage.
committed to nonvolatile storage.
Table C-9. Operational Modes
Mode
Description
Target
The desired mode of operation of the block.
Out of Service (
O/S
). The block is out of service, block execution is suspended,
and all output parameters take a status of
Bad::OutOfService
.
Initialization Manual (
IMan
). The block is in the process of initializing a cascade.
This is used for upstream (control) blocks when they are initializing for smooth
transfer into
transfer into
Automatic
mode.
Local Override (
LO
). Faultstate or an interlock is active and causing the output
value of the block to be overridden.
Manual (
Man
). The output value of the block is set by the user.
Auto (
Auto
). The output value of the block is set by the block to be equivalent to
the setpoint (SP) parameter of the block.
Cascade (
Cas
). The setpoint for the block is taken from the
CAS_IN
parameter.
This mode cannot be entered before cascade initialization takes place.
Remote Cascade (
RCas
). Like Cascade mode, in Remote Cascade mode the
setpoint of the block comes from an outside data source. Unlike Cascade mode,
in Remote Cascade mode the setpoint is sourced from the
in Remote Cascade mode the setpoint is sourced from the
RCAS_IN
parameter,
which is written by a host application and not another function block.
Remote Output (
ROut
). Remote Output mode is analogous to Remote Cascade
mode, except that the remote host application directly sets the output of the block
and not the setpoint. In the case of an analog output block, this bypasses setpoint
rate and absolute limiting.
and not the setpoint. In the case of an analog output block, this bypasses setpoint
rate and absolute limiting.
Actual
A bit reflecting the current state of operation of the block. This is a function of
the target mode and the current conditions in which the block is executing.
the target mode and the current conditions in which the block is executing.
Permitted
A bitmask indicating which modes are permitted target modes and which are not.
This could be used by the plant operator to disallow certain modes the block
would normally be permitted to have as a target mode.
This could be used by the plant operator to disallow certain modes the block
would normally be permitted to have as a target mode.
Normal
Not used by the block, this can be used by an operator to store the normal mode
of operation for the block in normal plant operations.
of operation for the block in normal plant operations.