PURPOSE: To prevent written data from being destroyed even when 'phase fluctuation is present by positioning the phase of a head for reading the data at an edge position for not crossing with a window.
CONSTITUTION: In a data changing circuit for writing the data delayed by a delay circuit 1 provided with a delay amount equal to or more than maximum phase fluctuation when the phases of input data and output data come close to a memory 5 and providing the phase margin of read and write, a large width window preparation part 10 for preparing a large width window whose width is wide, a large width delay window preparation part 11 for preparing a large width delay window for which the large width window is delayed for the delay amount of the delay circuit 1, a selector 14 for selecting the window and the large width window, the selector 15 for selecting a delay window and the large width delay window and a phase comparator circuit 12 with a previous frame for making input to the selector 8 the output of the selectors 14 and 15, comparing the phases of the head position of a present frame and the head position of the previous frame and controlling selection at the selectors 14 and 15 are provided.
HAYASHI AKIHIRO
OBA MASASHI
