| 摘要 |
PURPOSE:To set up storage capacity without depending upon a physical track by counting up index marks and generating a false index marker signal recognizing the initial and final ends of a logical track by a control device. CONSTITUTION:When a processor requests the reading of a logical cylinder No. (k), a logical track No. (n) and a record R, the control device positions an access arm to the cylinder No. (k) A signal from a control head is inputted to an index marker detecting circuit 11, which outputs an index marker and resets a sector counter 16. The circuit 11 outputs sector pulses and the counter 16 counts up the pulses. If it is supposed that the head is located on the position of sector (1)16 and ''1'' is set up in the counter 16, the control device reads out an end sector ''3'' from its internal table and sets up the sector in a comparison register 17. Subsequently, the control device reads out data from the head, and when the counter 16 counts ''3'', a false index marker is raised from a comparator 15, so that the initial and final ends of the logical track are recognized. |
