The Task Overrun error (%S19) is set to 1 when the time it takes to complete a Task exceeds the specified time.
The MAST & FAST Task's use the WDT setting to determine when %S19 will set. The user must reset this bit to 0.

Note : If this happens repeatedly, the program may be need to be reviewed. For instance, the program may have for loop in a ST section that does not exit the loop properly and that could cause a watchdog over run. If it is not the program then the Hardware needs to be set for a TEX.