Browse Prior Art Database

Timer to Sense an Incompleted Seek on Disk Files

IP.com Disclosure Number: IPCOM000094643D
Original Publication Date: 1965-Apr-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Kennedy, CJ: AUTHOR

Abstract

In disk file operation, the mechanical arm carrying a magnetic read-write head can move beyond the last usable track on the disk surface and reach a crash stop position. The distance between the last usable track and such position is too small to be sensed by a microswitch or photosensor. While the mechanical arm remains in the crash stop position, the disk file is not usable.

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Timer to Sense an Incompleted Seek on Disk Files

In disk file operation, the mechanical arm carrying a magnetic read-write head can move beyond the last usable track on the disk surface and reach a crash stop position. The distance between the last usable track and such position is too small to be sensed by a microswitch or photosensor. While the mechanical arm remains in the crash stop position, the disk file is not usable.

The circuit shown in A automatically senses a crash stop condition and corrects it. The maximum time required to locate a track in the disk file is 450 milliseconds. A single-shot (SS) 2 exhibits a time constant greater than the maximum time to locate a single track. A time constant of one second is provided in SS2. Each time a seek operation is begun, SS2 is turned on by a minus level busy latch signal on a line 4. Each time the track is successfully located, SS2 is turned off by a positive level busy latch signal on 4. However, in a crash stop condition, SS2 turns off while 4 remains at a minus level. Inverter 6 generates a minus level signal from the off condition of SS2 and applies this signal to minus And 8. Therefore, when the next sector pulse (SP) and pre-sector pulse (PSP) are sensed, lines 10 and 12, respectively, have minus level signals and the output of 8 goes positive. This positive signal is employed for retracting the mechanical arm to its normal position. The timing diagram for A is shown in B.

A second circuit for handling t...