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Tape Phase Error Detection Measurement

IP.com Disclosure Number: IPCOM000090201D
Original Publication Date: 1969-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Marcotte, DO: AUTHOR

Abstract

Functioning of phase error-detecting circuits for a phase encoded magnetic tape unit is checked by recording a sequence of worst case test data patterns, each of which includes an intentional dead track. Groups of records 10...16 are written, using blocks of different worst-case data patterns, such as 17 and 16, each of which is arranged to force a phase error. These worst-case patterns typically consist of intermingled long and short wavelength transitions, i.e., long-long-long-short, short-long-long-short, etc., as can force a phase error to occur. Phase errors occur when bits are detected during the window W transitions of the ramp generating oscillator and cause an error-detection indication.

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Tape Phase Error Detection Measurement

Functioning of phase error-detecting circuits for a phase encoded magnetic tape unit is checked by recording a sequence of worst case test data patterns, each of which includes an intentional dead track. Groups of records 10...16 are written, using blocks of different worst-case data patterns, such as 17 and 16, each of which is arranged to force a phase error. These worst-case patterns typically consist of intermingled long and short wavelength transitions, i.e., long- long-long-short, short-long-long-short, etc., as can force a phase error to occur. Phase errors occur when bits are detected during the window W transitions of the ramp generating oscillator and cause an error-detection indication. The records which are written include the forcing of a dead track, such as 19 and 20, for each track in sequence throughout the preamble, data pattern, and the postamble. This is accomplished by forcing the write circuitry for a selected track of the magnetic tape drive to fail to record data transitions for a preselected period of time.

In addition to the worst-case sequences, each data pattern forces a particular track to dead-track during the write operation as discussed. Then a read backward and read forward of the record is performed while a count of the detected phase errors is maintained for each operation. After all tracks are dead- tracked and read in the same manner, a summary is printed indicating the number of detected...