| 摘要 |
PURPOSE:To reset a microprocessor to the initial state at a program runaway time, by providing a means, which sets the voltage of a prescribed output port of the microprocessor to a low level by a certain timing during the execution of a program, or the like. CONSTITUTION:When the program is executed normally, instructions which make an output port 2 to low-level or high-level are executed in order, and the voltage at a point A does not exceed a certain value. However, if the program runs away and cannot get out of a main routine, instructions which make the port to low-level or high-level are not executed, and the voltage at the point A continues rising. As the result, a transistor 12 is turned on when the voltage at the point A is equal to the threshold voltage of an inverter buffer 13, and the voltage at the point A is reduced rapidly, and the voltage at a point B falls to 0V at once simultaneously. Then, a reset port 3 becomes temporarily lower than a prescribed voltage, and the state in the processor 1 is reset, and the runaway program is stopped and is returned to the start position. |
