Debugging
GF_ProjectVX code provides several debugging tools, which help the developer to check whether the application behaves as expected or not.All these debugging tools basically allow the developer to watch the value of selected variables while the PLC application is running.GF_ProjectVX code debugging tools can be gathered in two classes:
- Asynchronous debuggers. They read the values of the variables selected by the developer with successive queries issued to the target device. Both the manager of the debugging tool (that runs on the PC) and, potentially, the task which is responsible to answer those queries (on the target device) run independently from the PLC application. Thus, there is no guarantee about the values of two distinct variables being sampled in the same moment, with respect to the PLC application execution (one or more cycles may have occurred); for the same reason, the evolution of the value of a single variable is not reliable, especially when it changes fast.
- Synchronous debuggers. They require the definition of a trigger in the PLC code. They refresh simultaneously all the variables they have been assigned every time the processor reaches the trigger, as no further instruction can be executed until the value of all the variables is refreshed. As a result, synchronous debuggers obviate the limitations affecting asynchronous ones.