Circuit and methodology for reading and tracking binary data from magnetic tape independently of the data pattern on the tape
US4644420A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 29, 1984 |
| Grant date | Feb 17, 1987 |
| Priority date | — |
| Expiry date | Mar 29, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B20/1403
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Binary information recorded on magnetic tape is read from the tape and tracked in a manner which is independent of the data pattern on the tape. The time displacement error, TDE (used hereinafter interchangeably) between the data pulses from the tape and a phase-locked-loop reference signal is sampled and then held until the next subsequent opportunity at which the data from the tape can be updated. The TDE between a read binary one and a reference signal is measured by counting a plurality of reference pulses occurring between a reference edge marking the beginning of a data time window and the time at which a binary one is read from the tape. The accummulated count is sampled by a counter whose contents are then stored in a latch when the total TDE has been measured. The TDE in the latch is then used in the phase-locked-loop circuit to adjust the frequency of the reference signal to more nearly match the frequency of the data read from the tape. Thus, whenever a binary one is read from the tape, the TDE is measured, stored and used until the next binary one is read and the time displacement error can then be updated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.