| 摘要 |
A control unit for supervising operation of data transmission to and from a data storage device such as a disk storage device, has a stored program for the unit, and a random access memory sufficient to store an entire block of data received from the data storage device. In one arrangement, the control unit works in conjunction with external data processing apparatus, and the control unit controls interchange of data between the data processing apparatus and the data storage device. The external data processing apparatus has a reduced memory capacity requirement, because of the control unit, and delays caused by static timing requirements are minimized. When the data storage device is a disk storage device, reading is performed without delay, using the first available sector of the disk in a given track. The random access memory stores the identity of the sectors which have been successfully read in the current operating sequence, so that, at the beginning of any such sequence, the first available unread sector is read and processed, irrespective of the position of such sector relative to the previously read sector. Data processing operations are completed by the control unit within the intersector gap which separates two sectors of recorded data, so that an entire track can be processed in a single disk rotation, if no writing is required. During a track selection operation, the control unit operates the track selecting mechanism slightly faster than the selecting mechanism's maximum operating speed, and repeats the track selection operation until the desired track is selected, thus avoiding delays. Because of the speed of operation of the disk controller, and the completeness of its performance, the time required for interrupts in the programs of the external data processing apparatus is materially reduced, and the capacity required of an external processor, for any application, is also much smaller.
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