![]() ![]() (The application has control over which tags are OPC_WRITEABLE.) ![]() Callback notification is provided for any Process Tag that is modified by an OPC Client connection. The controlling application may change the value of the data at any time, and all attached clients would be automatically notified. The DLL records the data point and makes it available to any OPC Client application by name. The controlling application creates Process Tags by passing a name and value to the DLL. WTOPCSvr basically operates as a data librarian. All required OPC Interfaces are supported for both OPC 1.0 and OPC 2.0 Data Access Standards as well as the Browse Interface. The DLL may be easily integrated with existing applications, or new ones. All the details of COM and OPC are handled by the DLL, which allows an application to present data points to OPC at a high-level, without having to be concerned with the actual implementation of the underlying interfaces. For example, an OPC Client can support OPC DA (Data Access), OPC HDA (Historical Data Access), OPC A&E (Alarms & Events), and even OPC UA (Unified Architecture) inside the same software application.The WinTECH Software Rapid Development DLL for OPC Servers, (WTOPCSvr), provides an easy to use API for integrating custom data with OPC. In addition, OPC Clients can handle multiple OPC specifications simultaneously. OPC Clients can handle an unlimited number of OPC Server connections. ![]() When OPC Clients and Servers are used together, they can be used for supervisory control and data acquisition (SCADA). This enables the HMI to provide supervisory control setpoints in the OPC Server, which, in turn, sends the setpoints to the underlying control system (PLC or DCS). HMI applications are typically programmed with OPC Clients. OPC Client applications can also be used for supervisory control. Software applications can then archive data from a PLC, DCS, process analyzer, etc. In this scenario, they simply subscribe to data (or poll data) from an OPC Server and either display or archive the data, or even both. OPC Client applications can be used for data acquisition. OPC is based on client/server architecture. An OPC Client is a software module that enables applications to acquire data from an OPC Server or conduct supervisory control using an OPC Server. ![]()
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