| 摘要 |
PURPOSE:To improve the reliability of a magnetic disk device by preparing the spare magnetic head and recording surface and providing a function to switch automatically a specific magnetic head or recording surface to a spare one by a command of an upper device in case read errors are frequently produced from said specific head or surface. CONSTITUTION:For instance, the preceding defects are frequently produced to a recording surface corresponding to a head HD2 and no spare track is available any more. In such a case, an upper device sends a head address register set conversion signal 16 to a head address conversion circuit 5. The circuit 5 receives a head address signal 12 from a head address register 6 and at the same time converts the signal 12 so as to energize the signal HSS in place of the signal HS2 among head selection signals 11. Thus a head selection circuit 4 selects a spare head of head number HDS. |
