Echelon OpenLNS User Manual

Page 1035

OpenLNS Programmer's Reference

998

shared by connections that intersect each other. This error will be generated when an

attempt is made to form a connection that violates this constraint, and no network

variable alias was available to overcome the constraint. If network variable aliases are

available on the devices in the connection, they will normally be automatically used to

avoid this error.
A selector is a number assigned to the network variable during the connection process in

order to identify connected network variables. All members of the same connection, and

any intersecting connections, share this selector. Without aliases, if an attempt is made

to connect several inputs or several outputs (one or more of which polled by an input) on

the same node in the same connection (or intersecting connections), this error will be

generated. The use of aliases allows a single connection of several intersecting

connections to have several different selectors (one per alias). If aliases are available,

this error will normally not occur.
lcaErrConnNoMoreAddressSlots

This error will occur when a device involved in an attempted connection does not have an

available address table slot to complete the connection. This can also occur when

multiple connections are sharing an address table slot, and one of them changes. As a

result, they can no longer share address table slots.
In some cases broadcast addressing can be used to reduce address table usage, because

output connections to different nodes may be able to use the same broadcast address

table entry. In addition, if the connection is a multicast connection, the use of broadcast

addressing will not require a group address table entry on the target device. The use of

broadcast messaging is controlled by the BroadcastOptions property of the

ConnectDescTemplate object being used by the connection.
In some cases, aliases may be used to shift address table entry usage from one device to

another. Multicast messages using a group use one address table entry on the source

device, and one on each target device (note that this address table entry may be used for

other connections as well). Using aliases to support multicast will result in using an

address table entry for each target on the source node, but require no address table

entries on the target node. The use of aliases for multicast is controlled by the

AliasOptions property of the ConnectDescTemplate object.
lcaErrConnCannotCreateGroup

This error will occur when the requested connection requires a group, but there are no

more groups available in the domain.
A domain can contain 256 groups. Groups and group membership are assigned when

connections are created. If there are several targets within a connection, a group will

normally be formed. The use of aliases may prevent a group from being used, and

broadcast addressing can be used as an alternative to groups. Use of aliases for

multicast and broadcast can be controlled via the AliasOptions and BroadcastOptions

properties of the ConnectDescTemplate object being used by the connection.
Groups can be reused for multiple connections within the same domain. Connection

timers used by the different connections must be compatible, and the collection of nodes

must either be identical in all the connections, or all the connections must at least have

the same set of destination nodes (the sources can be different). This last case is called

group overloading. Reusing groups is done automatically with the OpenLNS Object

Server.
lcaErrConnNoMoreNetvarSelectors

An attempted connection failed because all network variable selector values were in use.