| 摘要 |
PURPOSE:To detect a write state to a test area and to protect completely the write state by adding a means to a magnetic disk device to inhibit the writing carried out from a host device as necessary. CONSTITUTION:Both upper and lower limit inhibiting areas are stored in the upper and lower limit address memory circuits 11 and 12 of a write protection system respectively. Then the read or write address designated by a host device is stored in a read/write address memory circuit 20. An upper limit comparator 31 compares the contents of both circuits 11 and 20 with each other, while a lower limit comparator 32 compares the contents of both circuits 12 and 20 with each other. An AND circuit 40 secures an AND between outputs of both comparators 31 and 32, and a read/write indicating circuit 50 indicates the distinction between the read and write states. An AND circuit 60 secures an AND between the outputs of both circuits 40 and 50, and a valid/invalid indicating circuit 70 indicates the valid or invalid of each action. Then an AND circuit 80 secures an AND between both circuits 50 and 60. The circuits 40, 60 and 80 detect the write state to a test area for complete protection of the write state. |
