The compiler enables you to write your own exception programs for handling particular system events. The following exceptions can be handled:
- Startup (before the first cycle)
- Shutdown (after the last cycle)
- Division by zero
Startup
You can write your own exception program to be executed before the first application cycle is executed:
1- Create a new main program that will handle the exception. It
cannot be a SFC program.
2- In the editor of global defines,
insert the following line:
#OnStartup ProgramName
Warning: The program is executed before all other programs within the fisrt cycle. This implies that the cycle timing may be longer during the first cycle. You cannot put breakpoints in the Startup program.
Shutdown
You can write your own exception program to be executed after the last application cycle when the runtime system is cleanly stopped:
1- Create a new main program that will handle the exception. It
cannot be a SFC program.
2- In the editor of global defines,
insert the following line:
#OnShutdown ProgramName
Warning: You cannot put breakpoints in the Shutdown program.
Division by zero
You can write your own exception program for handling the "Division by zero" exception. Below is the procedure you must follow for setting an exception handler:
1- Create a new sub-program without any parameter that will
handle the exception
2- In the editor of global defines,
insert the following line:
#OnDivZero SubProgramName
In the sub-program that handles the exception you can perform any safety or trace operation. You then have the selection between the following possibilities:
Return without any special call. In that case the standard handling will be performed: a system error message is generated, the result of the division is replaced by a maximum value and the application continues.
Call the FatalStop function. The runtime then stops immediately in Fatal Error mode.
Call the CycleStop function. The runtime finishes the current program and then turns in "cycle setting" mode.
Handlers can also be used in DEBUG mode for tracking the bad operation. Just put a breakpoint in your handler. When stopped, the call stack will show you the location of the division in the source code of the program.