Echelon LNS DDE Server - Manual (Page 72)

Specifying a Network Variable
Monitoring and control applications will typically monitor input or output network
variable values and allow an operator to update input network variable values.
Network variables may be identified either by member name within a L
ON M ARK
object, or by name for a device. Devices with L ON M ARK objects may have multiple
network variables with the same name, so using the L ON M ARK object name/member
name is a more reliable way to access network variables on L ON M ARK -compatible
devices. To access a network variable, you must select the naming method in the
DDE Topic, and the specific network variable in the DDE Item. The NV and Netvar
topics are provided for backward compatibility with applications developed for the
16-bit LonManager DDE Server.
Specifying a Network Variable Topic
A network variable topic is specified using the standard topic format or custom topic
format described in Chapter 4. The topic type will be one of the following network
variable topics:
Category Topic Type Description
Network
Variable
LMNV Network variables belonging to a L ON M ARK object. Use
this type to access network variables belonging to a
specific L
ON M ARK object. The item name must specify
both the device name and the L ON M ARK object name.
DevNV Network variables on a device. This type accesses
network variables on a device that are not
configuration properties and not members of a
L ON M ARK object.
Netvar or
NV
All network variables on a device. Provided for
backward compatibility with the 16-bit LonManager
DDE Server. A network variable accessed through this
type may in fact be a configuration property or a
network variable that belongs to a L ON M ARK object
present in the device. Devices with L ON M ARK objects
may have duplicate network variable names when
accessed using this topic. The LMNV or DevNV topic
should be used instead.
Specifying a Network Variable Item
A network variable item identifies a device and a network variable or network
variable field on the device. It also specifies a L ON M ARK object if the L ON M ARK
object/member name method is used to identify the network variable. The format for
specifying this information is the following:
device_name[.lm_name].nv_name[[.array_index]][.field_name] [parameters]
5-2 Reading and Writing Network Variables