| 摘要 |
PURPOSE:To monitor the abnormal state of a device which controls a stepping motor by monitoring a driving circuit of the stepping motor to inhibit a reset pulse outputted to a watchdog timer. CONSTITUTION:An edge detecting circuit 3 of a watchdog timer 2 detects the edge of a pulse inputted from a microcomputer 1, which controls a stepping motor 22, to output the reset signal to a counter 4. The counter 4 counts the output of an oscillation circuit 5; and when the period of the pulse of the microcomputer 1 is longer, Qn is '1' to reset the microcomputer 1. A comparator 23 compares the number of turned-on transistors TRs out of driving TRs 18, 19, 20, and 21 with a reference value of a comparison reference value setting part 24, and the comparator 23 outputs the low level if the comparison reference value is smaller. An AND circuit 25 inhibits the pulse outputted from the microcomputer 1 to the watchdog timer 2. |
