Browse Prior Art Database

Write Checking Using Cyclic Redundancy Checks

IP.com Disclosure Number: IPCOM000077624D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hall, PH: AUTHOR

Abstract

It is desired to enhance verification that signals being recorded on a magnetic tape have actually been satisfactorily recorded. Those tape recorders having a plurality of CRC (cyclic redundancy check) circuits such as shown in U. S. Patent 3,508,194, verify recording using residue checking methods.

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Write Checking Using Cyclic Redundancy Checks

It is desired to enhance verification that signals being recorded on a magnetic tape have actually been satisfactorily recorded. Those tape recorders having a plurality of CRC (cyclic redundancy check) circuits such as shown in U.
S. Patent 3,508,194, verify recording using residue checking methods.

Input signals are supplied through write circuits to be recorded on magnetic tape moving past a read/write head. Write gaps are the upstream gaps in a normal two-gap-per-track tape subsystem. Simultaneously with providing recording signals, write circuits supply data signals to CRCW for generating a CRC residue check. The residue check is generated until a stop-write command has been received from the connected CPU, not shown. CRCW then holds the residue until completion of read-after-write.

Read-after-write portion (RAW) includes supplying control signals to the read circuits and CRCR circuits for checking signals read from the tape during RAW. Theoretically, CRCW should generate the same check bit residue as CRCR. Read circuits will be reading signals previously recorded on the tape for some time after the stop-write signal has been received. Read circuits detect end-of- record (EOR) by loss of envelope in a plurality of tracks. EOR signal activates CONTROL CIRCUITS to terminate operation of CRCR, cause a transfer of CRCW and CRCR residue contents to the compare circuits. Then, a test is initiated with results of the tes...