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Print Line Buffer Error Recovery

IP.com Disclosure Number: IPCOM000074335D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Frassetto, HE: AUTHOR [+2]

Abstract

A new approach to automatic error recovery within a printer control unit uses a new bit designated as "Character Not Printer" (CNP).

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Print Line Buffer Error Recovery

A new approach to automatic error recovery within a printer control unit uses a new bit designated as "Character Not Printer" (CNP).

Within the Control Unit a redundant image of the line to be printed is stored in a Page Reprint Buffer (PRB), which is also used for other functions. During a print operation the parity of each data character from the Print Line Buffer (PLB) is checked when it is accessed for comparison with the type train characters. At this point, if an error is detected, the print hammer for that position is prevented from firing and the PLC bit is set on in a Print Line Check plane. The position in error is denoted by a new bit called Character Not Printed (CNP). This CNP bit is set on in one of the check planes. The printing process will continue, ignoring the position with the CNP bit on, while the control unit corrects the character in error. The correction is accomplished by replacing the error character with the character from the corresponding position in the Page Reprint Buffer. When the data is restored, the CNP bit and the PLC bit will be reset. On subsequent scans the corrected character will be optioned to print, since the PLC bit was reset.

This technique allows continuation of the users job, without operator or system intervention, thus making the error transparent to the operator or system. While the use of a redundant image of the print line has been described, the actual correction could be accomp...