PLC Operation Control via System Variables

Caution

You are responsible for runtime system services being enabled under safe application conditions and disabled only under critical conditions.

At runtime, the state of an application or facility can become sensitive and disruptive actions can endanger the entire machine or facility. However, in this state you can suppress certain commands and prevent dangerous actions. The PlcOperationControl function block and Component Manager library are provided for this purpose.

Examples of CODESYS commands that can suppress operations when executed:

  • Online Change, Download
  • Enable Breakpoint
  • Reset Application, Stop Application
  • Transmit Data
  • Force Values, Write Values

In order that a backup solution is always in place, you are not permitted to suppress the Reset origin and Delete commands.

CODESYS will notify you if a currently disabled runtime system service is required when the application is in runtime mode. Then, you can respond with an appropriate countermeasure.

Function Block PlcOperationControl for Operation Control

This function block is used for enabling and disabling operations.

Property (PROPERTY)
Name Data Type Initial value Description
xDisableApplicationOnlineChange BOOL FALSE TRUE: Online change is suppressed.
xDisableApplicationDownload BOOL FALSE TRUE: Download is suppressed.
xDisableApplicationStop BOOL FALSE TRUE: Application stop is suppressed.
xDisableApplicationBP BOOL FALSE TRUE: Setting breakpoints is suppressed.
xDisableApplicationWrite BOOL FALSE

TRUE: Writing variables is suppressed.

This can also be suppressed via PLCHandler/IecVarAccess.
xDisableApplicationForce BOOL FALSE TRUE: Forcing variables is suppressed.
xDisableApplicationReset BOOL FALSE TRUE: Resetting the application (not “Reset origin”) is suppressed.
xDisableAll BOOL FALSE TRUE: All operations are suppressed.

Implementing Operation Control

Requirement

  • Compiler version >= 3.4.3.0
  • In the device description, the PLC operation control is enabled by system variables.

  1. Declare an instance of the PlcOperationControl function block (for example, PlcOpCtrl_Inst).

    ⇒

    PlcOpCtrl_Inst : PlcOperationControl;

  2. Suppress a command by assigning the respective TRUE property (for example, “Stop Application”.

    ⇒

    PlcOpCtrl_Inst.xDIsableApplicationStop := TRUE;

See also