Echelon OpenLNS - Manual (Page 196)

OpenLNS Programmer's Reference 159
organization at the time. As a result, LNS 3.20 allows
applications such as device plug-ins to modify the constant
attribute by writing to this property. Set this property to
True to turn on the constant attribute. Set this property to
False to turn off the constant attribute.
When modifying this property, you should note that some
configuration properties are stored in non-writable storage,
such a ROM. In this case, OpenLNS cannot verify whether it
is possible to update the value or not. If an OpenLNS
application sets the constant attribute to False, and that
configuration property’s value is stored in non-writable
memory, updating the value in the device will fail. The
failure may or may not be reported to LNS and to the
OpenLNS application, depending on how the value is stored.
Even if the value is stored in modifiable memory, such as
flash, it may be part of the checksumed application area. If
this is the case, modifying the value may cause the device to
detect an application checksum failure and enter the
applicationless state. In addition, it is not possible for LNS to
determine whether or not the device will operate correctly if
the configuration property value is successfully modified in
the device. For these reasons, you should take extreme care
when modifiying this property from its initial setting, and
only modify it if you have intimate knowledge of the device
application, and are certain you can successfully update the
value of the configuration property.
For more information on configuration property attributes,
see the Configuration Property Flags section of the LonMark
Application-Layer Interoperability Guidelines.
Availability Local, full, and lightweight clients.
Syntax returnValue = cpObject.ConstantAttribute
Element Description
returnValue A Boolean value indicating whether or
not the constant attribute flag of the
configuration property is set. If this
property is set to True, then the
attribute is set.
cpObject The ConfigProperty object being acted
on.
Data Type Boolean.
Read/Write This property is read-only for ConfigProperty objects that are
accessed through AppDevice objects.
This property is read/write for ConfigProperty
objects
accessed through DeviceTemplate objects. Modifying this
property for a ConfigProperty on a DeviceTemplate will affect
all devices using that template.
Added to API LNS Release 3.20.