Echelon LonTal Stack - Manual (Page 178)

166 Appendix C: Appendix C
Neuron C Syntax for the
Model File
In an application that uses compiler-generated SD data, you can still specify
additional SD data with the sd_string() modifier. The compiler appends this
additional SD information to the compiler-generated SD data, but it will be
separated from the compiler-generated information with a semicolon. SD
data that appears after the semicolon is treated as a comment and is not
included in the device’s interoperable interface.
The Network Variable Storage Class
Network variables constitute one of the storage classes in Neuron C. The
optional storage-class specification for a network variable includes the following
keywords:
const
Specifies a network variable that cannot be changed by the application
program. Output network variables declared with const can be placed in
PROM or EPROM. Input network variables declared with const can be
updated over the network, and should therefore be placed in RAM.
When const is used with output network variables, the polled modifier
should also be considered.
Important: If specified, the const keyword must appear as the first
keyword for the network variable declaration in a model file. For example:
const network output polled SNVT_address nvoFileDir;
eeprom
Allows the application program to indicate network variables whose values
are stored in non-volatile memory and therefore are preserved across power
outages.
config
This modifier is obsolete and has been replaced by the config_prop keyword.
config_prop | cp
This keyword declares the network variable to be a configuration property.
If no class is specified for a network variable, the network variable is a global
variable. Global variables should be stored in RAM and need not be
preserved across power outages.
The Network Variable Type
Network variable types serve two purposes. First, typing ensures proper use of
the variable in the device's application. Second, typing ensures proper connection
of network variables so that a sending device and a receiving device can agree on
the representation of data within the network variable. A network variable can
be declared using any of the following types:
• A standard network variable type (SNVT) or standard configuration
property type (SCPT) defined in the standard resource file. You can use
the NodeBuilder Resource Editor to view all available SNVTs and SCPTs,
along with their definitions.