Echelon Neuron C - Manual (Page 110)

98 Using Configuration Properties to Configure Device Behavior
requirements of all individually listed FPT members (for example, same
type, same array size, and so on).
9 A single configuration property that inherits its type from a network
variable cannot be shared simultaneously by both changeable and non-
changeable network variables.
Type-Inheriting Configuration Properties
You can define a configuration property type that does not include a complete
type definition, but instead uses the type definition of the network variable to
which it applies. A configuration property type that uses another variable’s type
is called a
type-inheriting configuration property .
A typical use for type-inheriting configuration properties is for value limiting
configuration properties. Configuration properties that describe a network
variable’s minimum or maximum values, or threshold or hysteresis levels, for
example, need not be defined for every possible network variable type. Instead,
such a configuration property is fully described by its semantics, and through the
item to which it applies.
When the CP family member for a type-inheriting configuration property appears
in a property list, the instantiation of the CP family member uses the type of the
network variable. Likewise, a configuration network variable can be type-
inheriting, but each element of a configuration network variable array must
inherit the
same type.
Because the type of a type-inheriting configuration property is not known until
the instantiation, the configuration property initializer option can only be
provided in the property list rather than in the declaration. Likewise, different
range-mod strings may apply to different instantiations of the property, and
therefore, for a type-inheriting configuration property, the range-mod option can
only be provided in the property list, rather than in the declaration.
Shared configuration network variables (see the preceding section on that topic)
that are also type-inheriting can only be shared among network variables of
identical type.
A type-inheriting configuration property cannot be used as a device property,
because the device has no type from which to inherit. It should be noted that
type-inheriting configuration properties can apply to network variables or to
functional blocks, but not to the device. In the case that a type-inheriting
configuration property applies to a network variable explicitly, it derives its type
from the network variable. In the event that the type-inheriting configuration
property applies to the entire functional block, the property derives its type from
the functional block’s principal member network variable.
Each functional profile should have one member network variable designated as
the principal member network variable. The profile must define a principal
network variable if type-inheriting configuration property members exist that
apply to the entire profile. Type-inheriting configuration properties can be
shared among multiple network variables or multiple functional blocks, but the
types of the network variables to which the type-inheriting configuration
property explicitly or implicitly applies must all be the same.
A typical example of a type-inheriting configuration property is the
SCPTdefOutput configuration property type. The SFPTopenLoopSensor