Patent ID: 7612517

Claim:
A stepping motor controller comprising: a pulse frequency adjustment circuit that receives a command pulse having a first frequency from an external controller that outputs the command pulse in accordance with an interrupt process performed periodically by the external controller, and generates an alternative command pulse having a second frequency that is lower than the first frequency, wherein the second frequency is generated based on a reference clock pulse having a predetermined frequency generated by a reference clock generation unit; and a motor driving circuit that receives the command pulse through the pulse frequency adjustment circuit, and controls a stepping motor to rotate on the basis of the command pulse, wherein the pulse frequency adjustment circuit outputs the alternative command pulse to the motor driving circuit instead of the command pulse received from the external controller, when the first frequency exceeds a predetermined level, wherein the pulse frequency adjustment circuit comprises: a first counter that counts a first pulse number of the command pulse received from the external controller; a second counter that counts a second pulse number of the reference clock pulse generated by the reference clock generation unit; a pulse generation unit that generates the alternative command pulse having the second frequency based on the reference clock pulse generated by the reference clock generation unit; a determination unit that determines whether to output the alternative command pulse to the stepping motor instead of the command pulse received from the external controller, by comparing the first pulse number and the second pulse number; and a switch unit that outputs one of the command pulse and the alternative command pulse to the motor driving circuit in accordance with the determination made by the determination unit.