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Function Codes
Example:
Ahighlevelanaloginputsignalhasarangeof0to10VDC.Theactualinput
signal is at 5 VDC. The engineer ing unit associated with the input is percent
(%); therefore, the high limit is 100 and the low limit is zero. For this signal, the
I/O block will report the input value as 50 percent.
Alarm limits and significant change are expressed in engineer-
ing units.
I/O Source
There are three input or output source selections for each I/O
channel: normal, override, and simulated. The source is
selected by setting certain I/O channel function code specifica-
tions (refer to Table 6-2). A value or state is identified as either
normal, simulated, or overridden when reported. Additionally,
an I/O channel can be undefined. An undefined channel is
ignored during control configuration execution.
NOTE: The override, simulation, and status error inhibit permit specification
(S26) in the I/O device definition function code acts as the master switch for
enabling or disabling the override and simulation I/O source options for individ-
ual channels.
Normal
The I/O source is normal as long as the override, simulation,
or undefined options are not selected. Normal is the default.
Override
The override option allows the I/O channel value or state to be
manually overridden (locally substituted) to support system
checkout or field testing. An override enable specification con-
trols the override function and an override value specification
sets the substitute value. The value specification is tunable
and can be changed from a human system interface or by
another function code.
Simulation
The simulation option allows the I/O channel value or state to
be simulated by some other function code. A simulation enable
specification controls the simulation function and a simulation
value specification selects the simulation value source.
NOTES:
1. An override value takes precedence over a simulated value, and both
override and simulated values take precedence over a normal input value.
2. Override and simulation modes do not function when the I/O channel is
set to undefined input.
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