At a Glance

When there is no watchpoint, the values of animated variables are displayed at the end of MAST task processing.

The limitation of this mode of operation is that it does not permit the value of a variable at a given point in the program to be known if this value is used in different sections.

The watchpoint is used to synchronize display of animated variables with execution of a program element (rung) in order to know their exact value at this specific point in the program.

Variables which are synchronous with the watchpoint must belong to the section in which the watchpoint is set; display of other variables is synchronous with the end of the MAST task.

These variables are displayed:

  • in the section ladder editor,

  • in the display window,

  • in a single animation table at a given moment when requested by the user.

NOTE: It is not possible to set a watchpoint in an event task.

Watchpoint Properties

These properties are:

  • the watchpoint can be set only in online mode; if the connection is broken, the watchpoint is lost as well,

  • a single watchpoint is allowed at a given moment; the watchpoint is exclusive with the breakpoint,

  • display of animated variables is effective before execution of the rung on which the watchpoint has been set,

  • a counter is incremented each time the rung with the watchpoint is executed, up to a maximum value of 9999, then reset to 0,

  • modification of a section is not authorized if a watchpoint is set.

How to Insert a Watchpoint

Carry out the following actions:

Step

Action

1

For example, select a contact in the rung.

2

Set the watchpoint in one of the following ways:

  • by selecting the following command from the menu:

    Debug->Set Watchpoint,

  • by selecting the following command from the contextual menu:

    Set Watchpoint,

  • or select the button in the toolbar.

Example:

NOTE: Inserting a new watchpoint automatically clears the old one.

How to Locate an Existing Watchpoint

Carry out the following actions:

Step

Action

1

Either:

  • by selecting the following command from the menu:

    Debug->Show Watchpoint,

  • or select the button in the toolbar.

2

The part of the language editor containing the watchpoint is displayed.

How to Synchronize with an Animation Table

Carry out the following actions:

Step

Action

1

Select the animation table desired.

2

either you can:

  • select the following command from the menu:

    Debug->Synchronize Animation Table.

  • or select the button in the toolbar.

How to Delete a Watchpoint

Either you can:

  • select the Debug->Clear Watchpoint command from the menu,

  • or select the button in the toolbar.