AdsClientAdsSymbolVersionChanged Event

C#

public event EventHandler<AdsSymbolVersionChangedEventArgs> AdsSymbolVersionChanged

Value

EventHandler AdsSymbolVersionChangedEventArgs

Implements

IAdsSymbolChangedProviderAdsSymbolVersionChanged

Remarks

In a Beckhoff TwinCAT system, the SymbolVersionChanged event is part of the ADS (Automation Device Specification) communication framework and is used to detect changes in the symbol table of a PLC. The SymbolVersionChanged event is triggered when the symbol table of a TwinCAT PLC changes and is meant as full reinitialization that invalidates all symbol/variable handles and notifications. This typically happens when:

• A new PLC program is uploaded.

Because online changes (minor edits) reorganizes the symbol table internally, they don't trigger the full reinitialization of variables and therefore not the SymbolVersionChanged event. Minor symbol changes may appear as Null Notifications (on Notification handles) or a AdsErrorCode.DeviceInvalidHandle in case of variable handles to indicate invalidated handle registrations. (The SymbolVersion counter doesn't trigger, when an online change is made on the PLC (ports 801, ..., 851 ...)).

Reference

AdsClient Class TwinCAT.Ads Namespace RegisterSymbolVersionChanged(EventHandlerAdsSymbolVersionChangedEventArgs) RegisterSymbolVersionChangedAsync(EventHandlerAdsSymbolVersionChangedEventArgs, CancellationToken) UnregisterSymbolVersionChanged(EventHandlerAdsSymbolVersionChangedEventArgs) UnregisterSymbolVersionChangedAsync(EventHandlerAdsSymbolVersionChangedEventArgs, CancellationToken)

Beckhoff Automation GmbH & Co. KG 2001-2026