Echelon LNS - Manual (Page 245)

LNS Programmer's Guide 231
with the configuration currently stored in the devices, even if database changes have
been made subsequently while the system management mode is set to
lcaMgmtModeDeferConfigUpdates
. The configuration of the permanent monitor sets
will not be updated to reflect the database changes until the management mode is
changed to
lcaMgmtModePropagateConfigUpdates
, at which point the devices will
also be updated. Thus, barring any update failures, the configuration of the monitor sets
will always be consistent with the physical devices on the network. As a result, you can
always use permanent monitor sets, regardless of the system management mode.
However, Echelon recommends that you use permanent monitor sets while the system
management mode is set to
lcaMgmtModePropagateConfigUpdates
whenever
possible.
You should also note that monitor points created or modified while in
lcaMgmtModeDeferConfigUpdates
mode cannot be used until the system is set to
lcaMgmtModePropagateConfigUpdates
mode. In addition, all connection changes
made while in
lcaMgmtModeDeferConfigUpdates
have no effect until the network is
placed in
lcaMgmtModePropagateConfigUpdates
mode.
Similarly, the implicit or explicit creation of bound connections causes device connection
changes that will not be propagated to the network while the system management mode
is set to lcaMgmtModeDeferConfigUpdates. As a result, your monitoring application
might fail to receive data, or it might have to resort to polling data. Echelon recommends
that you do not initiate bound monitor and control operations when the system
management mode is set to lcaMgmtModeDeferConfigUpdates.
Directly Reading and Writing Network Variables
At some point, you may want to read or write the value of a single network variable,
without monitoring its value before or after the operation. In this case, you should write
to the network variable directly, without creating a network variable monitor point.
Remember that if you plan on consistently monitoring and controlling a network variable
or group of network variables, monitor sets are the most efficient method to use.
Prior to LNS Turbo Edition0, the NetworkVariable object’s Value property was
provided for single read and write operations to network variables. However, as of LNS
Turbo Edition0, the Value property is deprecated and only supported for backwards
compatibility. You can now use the
GetDataPoint()
method to create
DataPoint
objects to read and write to the values of network variables. When you do so, your
application will have sole access to that data point, and it will manage the format of the
data contained in the network variable locally. As a result, it will avoid misinterpreting
any formatting changes that may be made to a network variable’s value by other client
applications.
To acquire a
DataPoint
object you can use to read or write to the value of a network
variable, follow these steps:
1. Acquire the
AppDevice
object containing the network variable you want
to modify.
Set MyAppDevices = MySubsystem.AppDevices
Set MyAppDevice = MyAppDevices.Item(“Device 1”)
2. Obtain the device’s
NetworkVariables
collection, and then get the
network variable you want to read or write.