Debug LD Programs

When power flow debugging Ladder Diagram (LD) programs, monitor the output values of elements. These values display using color, numeric, or textual values according to their data type:
  • Output values of Boolean type display using color. The output value color continues to the next input. When the output value is unavailable, Boolean elements remain black. The default colors are red when True and blue when False. Customize the colors used for Boolean items.
  • Output values of DINT, REAL, TIME, and MESSAGE type display as a numeric or textual value in the element. When the output is a structure type, the display value is the selected member.
When the output value for a numeric or textual value is unavailable, the
WAIT
 text displays in the output label. Transitional elements like Pulse rising edge (positive) contacts, with an unstable state, remain black. Values also display in the corresponding dictionary instance.
When the device is in the DEBUGGING state, perform one of these operations:
Task
Procedure
Change the cycle timing
  • From the
    Target Execution
     toolbar, set the required value in the
    Cycle Timing (ms)
     box fbd_ldr_stx_ct1.
Toggle the logical value of a contact, coil, or block input
  • Select the required element, then right-click
    Toggle Boolean Value
     (or press
    Ctrl+T
    ).
IMPORTANT: Set the
Generate debug information
 property to
False
 if a build error occurs when the
In-line
 property is
True
for LD function blocks.
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