PLC Programming

What is What in CoDeSys
Example of a LD network with an EN POU
2.3 Debugging, Online Functions...
Sampling Trace
Debugging
Breakpoint
Single step
Single Cycle
The Sampling Trace allows you to trace the value sequence of variables, depending upon the socalled
trigger event. This is the rising edge or falling edge of a previously defined Boolean variable
(trigger variable). CoDeSys permits the tracing of up to 20 variables. 500 values can be traced for
each variable.
The debugging functions of CoDeSys make it easier for you to find errors.
In order to debug, run the command 'Project' 'Options' and in the dialog box that pops up under
Build options select activate option Debugging.
A breakpoint is a place in the program at which the processing is stopped. Thus it is possible to look
at the values of variables at specific places within the program.
Breakpoints can be set in all editors. In the text editors breakpoints are set at line numbers, in FBD
and LD at network numbers, in CFC at POUs and in SFC at steps. No breakpoints can be set in
function block instances.
Single step means:
• In IL: Execute the program until the next CAL, LD or JMP command.
• In ST: Execute the next instruction.
• In FBD, LD: Execute the next network.
• In SFC: Continue the action until the next step.
By proceeding step by step you can check the logical correctness of your program.
If Single cycle has been chosen, then the execution is stopped after each cycle.
Change values online
During operations variables can be set once at a certain value (write value) or also described again
with a certain value after each cycle (force value). In online mode one also can change the variable
value by double click on the value. By that boolean variables change from TRUE to FALSE or the
other way round, for each other types of variables one gets the dialog Write Variable xy, where the
actual value of the variable can be edited.
CoDeSys V2.3 2-23