User manual

Klinkmann Automation SPA Bus Server 2
SPA Server Ver 1.x User Manual Rev 2.3 120XXM23
Communication Protocols
Dynamic Data Exchange (DDE) is a communication protocol developed by Microsoft to
allow applications in the Windows environment to send/receive data and instructions
to/from each other. It implements a client-server relationship between two concurrently
running applications. The server application provides the data and accepts requests from
any other application interested in its data. Requesting applications are called clients.
Some applications such as Wonderware InTouch and Microsoft Excel can simultaneously
be both a client and a server.
FastDDE provides a means of packing many proprietary Wonderware DDE messages
into a single Microsoft DDE message. This packing improves efficiency and performance
by reducing the total number of DDE transactions required between a client and a server.
Although Wonderware's FastDDE has extended the usefulness of DDE for our industry,
this extension is being pushed to its performance constraints in distributed environments.
The SPA Server “Suite Link & DDE version” supports the FastDDE Version 3 -- an
extension to Wonderware’s proprietary FastDDE Version 2. This extension supports the
transfer of Value Time Quality (VTQ) information. The original DDE and FastDDE Version
2 formats are still supported, providing full backward compatibility with older DDE clients.
FastDDE Version 3 works on Windows 9x systems as well as Windows NT systems.
NetDDE extends the standard Windows DDE functionality to include communication over
local area networks and through serial ports. Network extensions are available to allow
DDE links between applications running on different computers connected via networks
or modems. For example, NetDDE supports DDE between applications running on IBM
compatible computers connected via LAN or modem and DDE-aware applications
running on non-PC based platforms under operating environments such as VMS and
UNIX.
SuiteLink uses a TCP/IP based protocol and is designed by Wonderware specifically to
meet industrial needs such as data integrity, high-throughput, and easier diagnostics.
This protocol standard is only supported on Microsoft Windows NT 4.0 or higher.
SuiteLink is not a replacement for DDE, FastDDE, or NetDDE. The protocol used
between a client and a server depends on your network connections and configurations.
SuiteLink was designed to be the industrial data network distribution standard and
provides the following features:
- Value Time Quality (VTQ) places a time stamp and quality indicator on all data values
delivered to VTQ-aware clients.
- Extensive diagnostics of the data throughput, server loading, computer resource
consumption, and network transport are made accessible through the Microsoft
Windows NT operating system Performance Monitor. This feature is critical for the
scheme and maintenance of distributed industrial networks.
- Consistent high data volumes can be maintained between applications regardless if
the applications are on a single node or distributed over a large node count.
- The network transport protocol is TCP/IP using Microsoft’s standard WinSock
interface.
OPC (OLE for Process Control) is an open interface standard to provide data from a data
source and communicate the data to any client application in a common standard way.