Set the active topic configured in an alias topic

An active topic can be set programmatically by an OPC or a DDE client. The alias topic should be configured to Switch on Command. The following describes how each client can set the active topic.

DDE Client

These are two examples using Microsoft Excel VBA.

and

where:

RSLinx

is the DDE application name.

System

is a predefined topic of RSLinx Classic.

My_Alias

is the user configured alias name in RSLinx Classic.

KT_Topic

is the DDE topic that RSLinx Classic switches to.

Set_Alias(AliasTopic)

attempts to swap to the next topic.

also,

Set_Alias(AliasTopic,Topic2Swap2)

attempts to swap to Topic2Swap2.

OPC Client

You can swap alias topics from OPC, using a predefined @SwitchTopic item that can also be told what topic to switch to. This is swapped at when the item is started, and is not reswapped until it is stopped and started again. We recommend you create the item inactive, and perform an Asynchronous Read on it. There are two methods for calling it: