Echelon Neuron C - Manual (Page 202)

182 Functional Block Declarations
A Neuron C program can also implement additional network variables in the
functional block that are not in the list of optional members of the profile. Such
additional network variable members beyond the profile are called
implementation-specific members. These extra members are declared in the
member list using the implementation_specific keyword, followed by a unique
index number, and a unique name. Each network variable in a functional profile
assigns an index number and a member name to each abstract network variable
member of the profile, and the implementation-specific member cannot use any of
the index numbers or member names that the profile already uses.
Note that implementation-specific member network variables or configuration
properties can prevent device certification. Instead of adding implementation-
specific member network variables or configuration properties, consider removing
those items from the interoperable interface, or defining a user-defined functional
profile, possibly inheriting from a standard functional profile, and adding the
desired new members to that UFPT.
At the end of the member list there is an optional item that permits the
specification of a director function. The director function specification begins
with the director keyword, followed by the identifier that is the name of the
function, and ends with a semicolon. See the chapter on functional blocks in the
Neuron C Programmer’s Guide for more explanation and examples of functional
block members and the director function.
After the member list, the functional block declaration continues with the name
of the functional block itself. A functional block can be a single declaration, or it
can be a singly-dimensioned array.
If the fblock is implemented as an array, as shown in the example below, then
each network variable that is to be referenced by that fblock must be declared as
an array of at least the same size. When implementing an fblock array’s member
with an array network variable element, the
starting index of the first network
variable array element in the range of array elements must be provided in the
implements statement. The Neuron C compiler automatically adds the following
network variable array elements to the fblock array elements, distributing the
elements consecutively.
Example:
network output SNVT_lev_percent nvoValue[6];
// The following declares an array of four fblocks, which
// have members nvoValue[2]..nvoValue[5], respectively
fblock SFPTanalogInput {
nvoValue[2] implements nvoAnalog;
} myFB[4];
An optional external name can be provided for each functional block. An external
name can be specified with an external_name keyword, followed by a string in
parentheses. The string becomes part of the device interface that is exposed to
network tools. The external name is limited to 16 characters. If the
external_name feature is not used, nor the external_resource_name feature
described below, the functional block identifier (supplied in the declaration) is
also used as the default external name. In this case, there is a limitation of 16
characters applying to the functional block identifier.
An external name can optionally be specified using a reference to a resource file.
The reference is specified using the external_resource_name keyword, instead of