Abstract: A motor speed control having synchronous PWM signals has a synchronous phase detecting unit and a PWM control unit. The synchronous phase detecting unit detects the phase variation of a Hall signal, which represents the phase change of the motor, and outputs a digital value to the PWM control unit. The PWM control unit compares the digital value with a speed control command so as to obtain a PWM signal, wherein the PWM signal is synchronized with the Hall signal. Since the PWM signal is synchronized with the Hall signal, the motor is operated smoothly even in the low speed rotation, and audible noises are effectively reduced.

Abstract: A motor speed control having synchronous PWM signals has a synchronous phase detecting unit and a PWM control unit. The synchronous phase detecting unit detects the phase variation of a Hall signal, which represents the phase change of the motor, and outputs a digital value to the PWM control unit. The PWM control unit compares the digital value with a speed control command so as to obtain a PWM signal, wherein the PWM signal is synchronized with the Hall signal. Since the PWM signal is synchronized with the Hall signal, the motor is operated smoothly even in the low speed rotation, and audible noises are effectively reduced.

Abstract: A method for representing arithmetic values on which arithmetic operations can be performed uses operands having a fixed number of bits. In a first step, a plurality of operands are stored in a memory, wherein each operand has a bit pattern representing a particular value. In a second step, a tag associated with each of the operands is also stored in the same or a different memory. Each of the tags has a tag value that indicates whether or not its associated operand represents an ordinary operand value or a special operand value. If the operand represents a special operand value, the tag value also indicates which of a predefined set of special operand values is represented by the associated operand. A result of an arithmetic operation can be generated by, in a first step, inputting at least a first operand and a first tag to an arithmetic section.