Echelon Neuron C - Manual (Page 122)

110 Using Functional Blocks to Implement a Device Interface
1 Use the NodeBuilder Resource Editor to create a user functional profile
with the same functional profile key as the standard functional profile
that you want to inherit from.
2 Set Inherit Members from Scope 0 in the functional profile definition.
This setting makes all members of the standard functional profile part of
your user functional profile.
3 Add your additional members to the new user functional profile.
4 Declare a functional block based on the new user functional profile.
This method provides better documentation and easier reusability than using
implementation-specific members.
Accessing Members and Properties of a
Functional Block from a Program
You can access the network variable and configuration property members of a
functional block from a program just as you can access any other variable. For
example, members can be used in expressions, as function parameters, or as
operands of the address operator or the increment operator. To access a network
variable member of a functional block, or to access a network variable
configuration property of a functional block, the network variable reference can
be used in the program just as any other variable would be.
However, to use a CP family member, you must specify which family member is
being accessed, because more than one functional block could have a member
from the same CP family. The syntax for accessing a configuration property from
a functional block’s property list uses the Neuron C context operator, a double
colon, as follows:
fb-context :: property-identifier [ [ index - expr ] ]
fb-context : identifier [ index - expr ]
identifier
The particular CP family member is identified by a qualifier that precedes it.
This qualifier is called the context . The context is followed by two consecutive
colon characters, and then the name of the property. The context uniquely
identifies the property. For example, a functional block array, fba, with 10
elements, could be declared with a property list referencing a CP family named
cpXyz. There would then be 10 different members of the CP family cpXyz, all
with the same name. However, adding the context, such as fba[4]:: cpXyz, or
fba[j]:: cpXyz, would uniquely identify the CP family member.
Just like for network variable properties, even though a configuration network
variable can be uniquely accessed through its variable identifier, it can also be
accessed equally well through the context expression, just like the CP family
members.
Also, the network variable members of the functional block can be accessed
through a similar syntax. The syntax for accessing a functional block member is
shown below (the fb-context syntactical element is defined above):
fb-context :: member - identifier