Context

(TcoContext : ITcoContext)

API

TcoContext is an entry point for an application. It represents a station, functional unit, or a whole application. The Main method of the context is the root of the call tree.

TcOpen application requires to have at least one TcoContex.

Context can encapsulate units of different scope and size. Each context is an isolated island that manages only the objects declared within its declaration tree. Each TcoObject (more later) can have only one context. Inter-contextual access between the objects is not permitted. The context executes with Run method call from the PLC program. The Run method will take care of running Main method and other routines that are required for the context and its services.

Example of context implementation

Implementation of abstract TcoCore.TcoContext class

FUNCTION_BLOCK ExampleContext EXTENDS TcoCore.TcoContext
VAR    
    // State control variable
	_state : INT;    
    // Piston component
    _piston : Piston(THIS^); // About the construction via FB_init later.  
END_VAR

Implementation of abstract method Main

METHOD PROTECTED Main
//-------------------------------------------------------------
IF(_state = 0) THEN
    IF(_piston.MoveWork().Done) THEN
      _state := 10;
    END_IF;  
END_IF;

IF(_state = 10) THEN
    IF(_piston.MoveHome().Done) THEN
      _state := 20;
    END_IF;    
END_IF;
.
.
.
.
.
IF(_state = 20) THEN
    _state := 0;
END_IF;

Execution of the context. Here we call Run. It will implicitly call the Main method implemented have above.

PROGRAM MAIN
VAR
	_context : ExampleContext;
END_VAR
//-------------------------------------
_context.Run();