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Read Signal BOT EOT Detection on a Read Only Tape Drive

IP.com Disclosure Number: IPCOM000090006D
Original Publication Date: 1969-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Close, DK: AUTHOR [+2]

Abstract

The circuit eliminates the need for having permanent BOT Beginning of Tape or EOT End of Tape markers when reading tape. It generates an EOT pulse after the last record on tape is sensed during forward tape motion. It generates a BOT pulse after the first record on tape is sensed during backward tape motion. A Start Read pulse indicates that a tape is to be read. The leading edge of the Start Read pulse fires SS 1. Its output is inverted by Inverter 15 to block And's 16 and 17 during the time the tape accelerates and starts to read the first record. By this time a Read Envelope Signal generated from the read head signal actuates SSH 2. SS 1 and SSh 2 have a common Or'd output at point 14, which blocks And's 16 and 17.

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Read Signal BOT EOT Detection on a Read Only Tape Drive

The circuit eliminates the need for having permanent BOT Beginning of Tape or EOT End of Tape markers when reading tape. It generates an EOT pulse after the last record on tape is sensed during forward tape motion. It generates a BOT pulse after the first record on tape is sensed during backward tape motion. A Start Read pulse indicates that a tape is to be read. The leading edge of the Start Read pulse fires SS 1. Its output is inverted by Inverter 15 to block And's 16 and 17 during the time the tape accelerates and starts to read the first record. By this time a Read Envelope Signal generated from the read head signal actuates SSH 2. SS 1 and SSh 2 have a common Or'd output at point 14, which blocks And's 16 and 17. During the continuous forward tape motion, the SSH 2 holdover timing continues the blocking of And's 16 and 17 between records.

For start-stop operation, the Stop Motion Signal causes SSH 2 to block And's 16 and 17 during the stopped condition. The SSH 2 holdover time continues the blocking until tape is accelerated and reading the next record, so that the Read Envelope and SSH 2 signals can operate the blocking. The blocking of And's 16 and 17 continues until after the last record is read in either direction. On the next move backward or forward signal, both SS 1 and SSH 2 time out and drop to generate an EOT pulse from whichever of And's 16 or 17 is receiving the move signal. An EOT pulse is...