Abstract: Method and apparatus are provided for enabling a reproducing apparatus, having a read channel which utilizes a second transfer function, to recover accurately data which has been recorded on a medium with a first transfer function. A compatibility circuit (73) derives a data rate from the medium, and causes the read channel to sample the data steam acquired from the medium at a multiple of the data rate, thereby creating a multiply-sampled data stream. Further, the compatibility circuit manipulates the multiply-sampled data stream to generate a deformatted read data stream. In particular, a deformatter (62) of the compatibility circuit selects only some bits of the multiply-sampled data stream to generate a modified data stream; and the applies a reverse of the first transfer function to generate a deformatted read data stream.

Abstract: A system and method is provided for controlling a brushless DC motor (100), the motor being of the type having a plurality of coils (25, 26, 27) and a switching amplifier coil driving circuit (25A, 26A, 27A) including a plurality of transistors (21, 22, 29, 30, 33, 34). Current application to the plurality of transistors is controlled to obtain, near a commutation point of the motor, a simultaneous rise in current applied to a first of the transistors and a fall in current applied to a second of the transistors. Controlling application of current to the plurality of transistors involves, for each of the transistors, generating a PWM gate drive signal by selectively switching between a nominal PWM signal and a constant signal. The selective switching is in response to a synthesized state signal, the synthesized state signal being generated to alternate variably between the two states in accordance with a desired ramping of current to the first and second transistors.