OPC Interop Settings Add Compatibility for Non-Compliant Clients

Accessing OPC DA compliance settings in TOP Server

The OPC DA compliance settings in TOP Server are accessed through the Project Properties in the TOP Server Configuration interface.  Simply right-click on Project in the TOP Server configuration as shown to the right and select Properties.

In the Property Editor, go to the OPC DA section and scroll down to the Compliance settings. By default, all of these settings are configured for full OPC Foundation interoperability testing compliance.

OPC DA compliance settings and how they affect TOP Server OPC DA behavior

The following settings affect how TOP Server behaves when connected to an OPC DA client:

• Reject Unsupported Language IDs: Keep at the default of "Yes" to only allow Language IDs that are natively supported by the server. Set this setting to "No" to disable the compliant feature to force the server to accept any Language ID.
• Ignore Deadband for Cache Reads: Keep at the default of "No" to respect the deadband specified by the client application. Set to "Yes" to force TOP server to ignore the deadband setting on OPC groups added to the server. This is needed for some OPC clients when passing the correct value for deadband causes problems such as having "good" data even though it does not appear to be updating frequently or at all.
• Ignore Browse Filter: Keep at the default of "No" to respect browsing filters specified by the client. Set to "Yes" force TOP Server to return all tags to the OPC client application regardless of any browsing filters.
• Data Type Support for 2.05a: Keep at the default of "Yes" for TOP Server to adhere to the data type requirements and expected behaviors for data type coercion that were added to the 2.05a specification. Set to "No" to revert to data type support pre-2.05a as required by your client.
• Fail on Bad Quality: Keep at the default of "No" to remain OPC compliant and return success. Set to "Yes" to force TOP Server to return a failure if one or more items for a synchronous device read results in a bad quality read.
• Group Initial Updates: Keep at the default of "No"  to allow TOP Server to return initial updates as they become available. Set to "Yes" to force TOP Server to return all outstanding initial item updates in a single callback.
  • Setting to "Yes" may result in loss of buffered data when using drivers that support data buffering (Event Playback) for unsolicited device protocols.
• Respect Client Locale: Keep at the default of "Yes" for TOP Server to use the Locale ID of the OPC client when performing data type conversions. Set to "No" if you need TOP Server to use the Locale ID of the operating system instead.
• Bad Quality Item as S_FALSE: Keep at the default of "Yes" for TOP Server to return S_FALSE in the item error result for items without good quality to the client. Set to "No" to force TOP Server to use the legacy behavior of returning E_FAIL (0x80004005) as the error result.
• Return Data ASAP: Keep at the default of "No" to respect group update rate set by the client. Set to "Yes" to force a client update when an active item that experiences a change in value or quality regardless of update rate.