Database Server functionality

The Database Server provides different communication ways and is configured by a XML configuration file.

• Communication flow in two directions
• ADS_TO_DB
  Cyclic checking of a TwinCAT ADS device (e.g., TwinCAT PLC) and writing of these data to a "database"
• DB_TO_ADS
  Cyclic checking of a "database" (e.g., SQL database) and writing of these data to a TwinCAT-ADS device (e.g., a PLC) via ADS
• Configuration of the "TwinCAT Database Server" is based on an XML file. This configuration file describes the required "databases", ADS devices (e.g., PLC runtime systems), and variables.
  Two storage methods:
• "Double" The compatible variable data types are: BOOL, LREAL, REAL, INT, DINT, USINT, BYTE, UDINT, DWORD, UINT, WORD, SINT
• "Bytes" Compatible to all variable data types especially for strings and data structures

Two different function modes:

• AutoStart:
  Starts the cyclic checking of the PLC values from an ADS device (ADS_TO_DB) or the cyclic checking of a database (DB_TO_ADS) automatically, as soon as the TwinCAT System is an "RUN" - mode. The checking PLC program should be running as a bootproject.
• Manual:
  Functions like logging in a database or reading from a database could be started out of the PLC with function blocks.

The following diagram illustrates the server functionality.

The central unit of the TwinCAT 3 Database Server is the XML-Configuration file editor from which all needed options and configurations are made. The created Configuration could be used in two different modes (AutoStart/Manual). The TwinCAT 3 Database Server is the connective link between the PLC and the database.