Browse Prior Art Database

Recovery from Write Check Conditions

IP.com Disclosure Number: IPCOM000078722D
Original Publication Date: 1973-Feb-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Irwin, JW: AUTHOR

Abstract

In magnetic recording on flexible media, such as 1/2'' tape, a crease across the tape prevents recording in an area causing a write error or check condition. Additionally, because of various other operational conditions in a magnetic recorder, the signals recorded may result in marginal or low-amplitude readback signals. Such condition may also be regarded as a write error or write check condition. It is important that write retries are employed which reliably erase a poorly recorded record, and reliably rewrite or rerecord the data on the media in a downstream position.

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Recovery from Write Check Conditions

In magnetic recording on flexible media, such as 1/2'' tape, a crease across the tape prevents recording in an area causing a write error or check condition. Additionally, because of various other operational conditions in a magnetic recorder, the signals recorded may result in marginal or low-amplitude readback signals. Such condition may also be regarded as a write error or write check condition. It is important that write retries are employed which reliably erase a poorly recorded record, and reliably rewrite or rerecord the data on the media in a downstream position.

A long record, such as that illustrated above, includes preambles and postambles P bracketing data and resync portions D and R, respectively. The resync portions are constructed in accordance with U. S. patent 3,641,534. To accommodate most reliable retries, the length of the record being recorded is tabulated by counting resync portions R which represent fixed record portion lengths, plus counting the number of bytes in the last data portion D1. This count will yield the number of bytes or record positions in the record. The number of bytes in preambles and postambles p is added to the total count.

It is well known that digital tachometer signals, not shown, represent media displacement with respect to a transducer. The byte count also represents a given length on the media. The byte count is then converted into a tachometer count.

The retry after a detected recording error is initiated at head position A, by backspacing over the record based upon the tachometer count. This backspace control eliminates the need for sensing signals which may or may not be recorded on the media. At the end of the backspace, at position B, the tape is backhitched to position the erase head, not shown, immediately upstream of po...