Disk apparatus having signal processing unit

A signal processing circuit for converting a serial analog signal, obtained by sequentially reading data recorded on a disk by a head, to a parallel digital signal to be output, for converting an externally input parallel digital signal to a serial analog signal at the time of recording data on the disk, and for outputting the analog signal to the head, the signal processing circuit comprising:

• a converter for converting the serial analog signal of data read from the disk to a serial digital signal and for converting the parallel digital signal of externally input data to an analog signal in order to send the analog signal to the head;
• a shift register for converting the serial digital signal received from the converter to a parallel digital signal in a data read mode and for converting the parallel digital signal externally input to a serial digital signal to send the serial digital signal to the converter in a data write mode;
• a processor for operating faster than a disk access speed to perform a predetermined reading process on the parallel digital signal received from the shift register for sending the resultant read signal and for operating faster than the disk access speed to perform a predetermined writing process on the parallel digital signal externally input for sending the resultant write signal to the shift register;
• and
• a program memory, connected to the processor, for storing programs associated with the reading process and writing process that are performed by the processor.