Monitor the WDT timer instructions (p) number is FNC07 no operands, possession of 1 program step. WDT instruction function is to refresh the watchdog timer of the PLC.
FX series PLC watchdog timer default value is 200ms (D8000 could be used to set), normal PLC scan period is less than the scheduled time. If outside interference or the program itself that scan cycle is greater than the watchdog timer value, and PLC CPU error lights stopped working, can be at the right location and WDT instructions reset watchdog timer, so that the program can continue to the END.
As shown in Figure 1, using a WDT directive a 240ms program is divided, so that they are less than 200ms, you will no longer receive alarms stop.
WDT instruction should be used note:
1) if in the subsequent cycle of FOR-NEXT, the execution time may exceed the monitoring timer timing, WDT can be inserted in the loop.
2) and conditional jump instructions corresponding pointer before you label at CJ, CJ (the program jump back) it is possible to repeatedly jump between them repeatedly perform, execution time exceeded the monitoring time, CJ WDT is inserted between directive and the corresponding marking instructions
PLC ONE 
