Browse Prior Art Database

Velocity Compensated Recognition Of Decreasing Length Sectors On A Tape Storage Device

IP.com Disclosure Number: IPCOM000048690D
Original Publication Date: 1982-Mar-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Meier, RE: AUTHOR

Abstract

A tape storage device uses the ratio of tachometer counts from two reel to develop a radius factor for the motor control algorithm. The ratio count is used as an address offset to a motor radius table. This table contains the radius factors and sector numbers of the algorithm. The design of the table causes decreasing sector lengths as the sector numbers change when the tape is moving forward.

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Velocity Compensated Recognition Of Decreasing Length Sectors On A Tape Storage Device

A tape storage device uses the ratio of tachometer counts from two reel to develop a radius factor for the motor control algorithm. The ratio count is used as an address offset to a motor radius table. This table contains the radius factors and sector numbers of the algorithm. The design of the table causes decreasing sector lengths as the sector numbers change when the tape is moving forward.

When the tape is moving at high speed, the ratio counter is incremented by 2 counts at a time, as opposed to 1 count at normal speed. The resulting decreased resolution of the ratio counter at high speed, when considered with the decreasing tape sector size near end-of-tape (EOT), can have the effect of causing the system to jump a tape sector in this area.

To Improve the resolution of the forward motion with the EOT area, the high speed locate command can be forced into low speed operation at a tape sector number equal to approximately 80 percent, of the length of the tape as measured from beginning-of-tape (BOT). Backward motion may run at high speed In all areas of the reel of tape since the sector lengths are increasing.

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