Screen Scripts – which run only run when the associated Screen is displayed or are called by a Pushbutton on a Screen. Screen Scripts run on the Client.  Screen Scripts run at the frequency specified by the Graphic Parameters (Set Graph Param) as fast as every 25 milliseconds.
 

1. • Run Once when display first opened
   • Run continuously  while display is open by user
   • Run Once when display closed

The language of Advantech WebAccess/SCADA scripts is derived from TCL, an open-source scripting language commonly used for hardware-control programs.  Advantech WebAccess/SCADA scripts do not need to be compiled.

The components of a Advantech WebAccess/SCADA Script are grouped into five Areas:

1. 1. • ACTION – these are commands specific to Advantech WebAccess/SCADA. They are usually similar to keymacro and pushbutton commands. They address the need for scripts to interact with real-time data, controls and users.  For example, Alarm Acknowledge, GO TO a Graphic Display, Set a Value.  ACTION commands enhance the standard Tcl script commands.
      • KEYWORD – these commands are based on the Tcl programming language and introduce an "open  source" feature to Advantech WebAccess/SCADA scripts.  Many standard Tcl programs are the programming language of Advantech WebAccess/SCADA Scripts.  The language of Advantech WebAccess/SCADA scripts is derived from TCL, a scripting language commonly used for hardware-control programs.  This is the If, THEN, ELSE of a programming language. 
      • FUNCTIONS – these are mostly the advanced arithmetic functions (sine, cosine, rounding,  logarithmic functions)
      • OPERATORS – a simpler math operators (multiply, divide, addition, greater than, equal to, etc) and grouping characters (parenthesis, square brackets etc.)

Additional components of Advantech WebAccess/SCADA are the Tags (the real-time data) that  Advantech WebAccess/SCADA reads from Automation Equipment  and internal tags describing Advantech WebAccess/SCADA:

• IO TAGS – this is the real-time data collected from Automation Equipment such as PLCs, Controllers, VAVs, OPC Servers, etc.
• FIELD – these are Fields associated with IO TAGS, for example description, High Span, Alarm Limits, Alarms States etc.
• Daq TAG – these are internal system tags that describe the state Advantech WebAccess/SCADA , for example Serial Number, Last Button Pushed, communication port status.
• LOCAL TAG – These are user defined “screen tags” internal to Advantech WebAccess/SCADA and commonly used for display animation or reformatting data before presentation.

Please see Chapter 12 for detailed description of Scripts in Advantech WebAccess/SCADA.

The next section shows a Step-by-Step Guide of creating the most common screen script to Rotate a Fan or Pump based on the On/Off state of a Digital Tag.