OPC Historical Data Access Standards for communicating stored data OPC Security Standards for controlling client access to OPC compliant devices and systems OPC XML-DA Builds on the OPC Data Access specifications to communicate data in XML. Incorporates SOAP and Web services OPC Complex Data Standards for specifying the communication of complex data types such as binary data and XML The vast bulk of software which uses OPC is designed around the Data Access 2.0 specification (actually version 2.05a). These documents provide introductions to OPC Data Access: How to Use OPC Data Access (OPC DA) (from MatrikonOPC) A brief introduction to OPC Data Access (from CERN) OPC Data Access (OPC DA) Versions & Compatibility OPC provides standard specifications for data access (DA), historical data access (HDA), and alarms and events (A&E). These OPC specifications are widely accepted by the automation in-dustry. Classic OPC is based on aging Microsoft-COM/DCOM-technology,1) which has led to the development of new OPC Foundation specifications OPCXML-DAClientDriverHelp l Poll:Inthismode,nosubscriptioniscreated.Tagswillbereadfromtheserverattheinterval specifiedintheUpdateRateparameter. l Update/Pollrate Ethernet network distributed across the manufacturing enterprise. However, the OPC DA applications are only compatible with cooperating applications based on Microsoft Platforms. Secondly, the OPC XML-DA specification defines a new way to move the same type of plant floor data as the existing OPC COM-DA based products (The OPC Foundation, 2004 OPC DA Client API for LabVIEW toolkit provides all necessary OPC functions as a VIs to browse, connect, Read/Write tags from OPC servers using DA 2.XX and 3.0 interfaces. VIs use OPC .NET API provided by OPC Foundation ( opcfoundation.org ) to perform all functions described by OPC specification. My issue is that i'm working on a VB program to write OPC tags to a system that will only accept the value if the quality is "Bad - Not Connected" (00001000 binary). The VB program built so far can write the value to the appropriate tag but the quality is "Good" (11000000). Classic. Title: Data Access Description: The original OPC Specification and its evolution from versions 1, 2.x, and 3.0, covering: The concepts of OPC Client/Server technology and data definition. General activities which include defining an address space and browsing it, reading, writing, and subscribing for data update notifications. The OPC UA Online Reference is a searchable collection of specifications and information models. Information models are made available by publishing a index of types defined in the model as human readble tables. When possible the definition of a Type is linked to the appropriate section in the specification. cess OPC UA data. Let us compare that with the old and very successful OPC DA specification. This specification deals only with current data, not events, history or a rich information model and thus deals only with a subset of functionality pro-vided by the OPC UA specification. Nevertheless, the old OPC DA specification The OPC Foundation released the OPC XML DA specification as platform independent intermediate step, it was basically a WSDL. Now requiring a web server it turned out that implementation on small embedded devices reached only poor performance and wide adoption could not be reached. The need for a more general approach was born, generic and The OPC Foundation released the OPC XML DA specificatio