Echelon LonTal Stack - Manual (Page 74)

62 Creating a Model File
The L ON W ORKS file transfer protocol and the direct memory files features are
mutually exclusive; your device cannot implement both.
Responding to Configuration Property
Value Changes
Events are not automatically generated when a configuration property
implemented in a configuration file is updated, but you can declare your
configuration property so that a modification to its value causes the related
functional block to be disabled and re-enabled, or causes the device to be taken
offline and brought back online after the modification, or causes the entire device
to reset. These state changes help to synchronize your application with new
configuration property values.
Your application could monitor changes to the configuration file, and thus detect
changes to a particular configuration property. Such monitoring would be
implemented in the FTP server or direct memory files driver.
However, many applications do not need to know that a configuration property
value has changed. For example, an application that uses a configuration
property to parameterize an algorithm that uses some event as a trigger (such as
a network variable update or a change to an input signal) would not typically
need to know of the change to the configuration property value, but simply
consider the most recent value.
Defining a Configuration Property Array
You can define a configuration property as:
• A single configuration property
• An array of configuration properties
• A configuration property array
A single configuration property either applies to one or more network variables or
functional blocks within the model file for the device, or the configuration
property applies to the entire device.
When you define an array of configuration properties, each element of the array
can apply to one or more network variables or functional blocks within the model
file.
When you define a configuration property array, the entire array (but not each
element) applies to one or more network variables or functional blocks within the
model file. That is, a configuration property array is atomic, and thus applies in
its entirety to a particular item.
Assuming that the device has sufficient resources, it is always possible to define
arrays of configuration properties. However, configuration property arrays are
subject to the functional profile definition. For each member configuration
property, the profile describes whether it can, cannot, or must be implemented as
a configuration property array. The profile also describes minimum and
maximum dimensions for the array. If you do not implement the configuration
property array as the profile requires, the profile’s implementation becomes
incorrect.