| 摘要 |
PURPOSE:To adjust the timer time of a watchdog timer systematically by writing preliminarily a prescribed timer time extending instruction in accordance with the case where an element which increases the execution time of one cycle is added on a user program. CONSTITUTION:The watchdog timer of a programmable controller counts a preliminarily set certain time in response to a start signal given from a processor 1 to a watchdog counter 8. The processor 1 is reset when time counting is completed, and a time interrupting timer counts a certain time shorter than said time of the watchdog timer repeatedly by a time interrupting counter 9 and interrupts the processor each time when time counting is completed. If the prescribed timer time extending instruction is written preliminarily in a memory 4 in case that the element which increases the execution time of one cycle is added on the user program, the number of extensions is set to a reset number counter and the counter 8 is reset when the extending instruction is discriminated at the instruction execution time, and the reset number is counted down for every interruption from the counter 9 to perform the extension processing. |
