| 摘要 |
<p>A data separator system has a PLL circuit (25) for outputting data pulses (DP) and clock pulses (CP) on the basis of the read data (RD) from a magnetic recording medium. The system also includes an external synchronization detection circuit (2l) which detects the synchronization data (predetermined zero pattern data) recorded in the synchronization area of the magnetic recording medium (l3) on the basis of the read data (RD). When detecting the synchronization data, the synchronization detection circuit (2l) enables the PLL circuit (25) to oscillate in synchronism with the read data (RD). The data pulses (DP) and clock pulses (CP) output from the PLL circuit (25) are also supplied to an internal synchronization detection circuit (3l). On the basis of the data pulses (DP) and the clock pulse (CP), the internal synchronization detection circuit (3l) detects the synchronization data and upon detection thereof, a floppy disk controller (29) performs the data readout operation. The system further comprises a preventing circuit (25, 33 to 39) which prevents the PLL circuit (27) from performing the synchronizing operation to the read data, which is read out from the overwritten area in the magnetic recording medium (l3) by the preceding-erase type magnetic head.</p> |
