Echelon Neuron C - Manual (Page 111)

Neuron C Programmer’s Guide 99
functional profile is an example of a functional profile that lists the
SCPTdefOutput configuration property as an optional configuration property,
and it is used to define the default value for the sensor's principal network
variable. The SFPTopenLoopSensor functional profile itself, however, does not
define the type for the principal network variable.
The following example implements a SFPTopenLoopSensor functional block with
an optional SCPTdefOutput configuration property. The configuration property
inherits the type, SNVT_amp in this case, from the network variable it applies to
as shown below.
Example:
SCPTdefOutput cp_family cpDefaultOutput;
network output SNVT_amp nvoAmpere nv_properties {
cpDefaultOutput = 123
};
fblock SFPTopenLoopSensor {
nvoAmpere implements nvoValue;
} fbAmpereMeter;
The initial value (123 in the example) can only be provided in the instantiation of
the configuration property as discussed above, and not in the declaration,
because the type for cpDefaultOutput is not known until it is instantiated and
because it is a type-inheriting configuration property.
Type-Inheriting Configuration Properties for
Network Variables of Changeable Type
Type-inheriting configuration properties can also be combined with changeable-
type network variables; see
Changeable-Type Network Variables on page 68.
The type of such a network variable can be changed by a network integrator
when the device is installed in a network.
Example:
SCPTdefOutput cp_family cpDefaultOutput;
SCPTnvType cp_family cpNvType;
network output changeable_type SNVT_amp nvoValue
nv_properties
{
cpDefaultOutput = 123,
cpNvType
};
fblock SFPTopenLoopSensor {
nvoValue implements nvoValue;
} fbGenericMeter;
The nvoValue principal network variable, although it is of changeable type, must
still implement a default type (SNVT_amp in the example above). Because the
SCPTdefOutput type-inheriting configuration property inherits the type
information from this initial type, the initializer for cpDefaultOutput must
therefore be specific to this instantiation. Furthermore, the initializer must be
valid for this initial type.
Should the network integrator decide to change the type of the underlying
network variable at runtime to, for example, SNVT_volt, then it is the