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Browse Prior Art Database

Threshold Determination for Pel Memory Failures

IP.com Disclosure Number: IPCOM000049667D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Carnes, ML: AUTHOR [+4]

Abstract

Described is a procedure for establishing a failure threshold for a pel (picture element) memory that provides high quality printing with less than 100% operability.

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This is the abbreviated version, containing approximately 53% of the total text.

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Threshold Determination for Pel Memory Failures

Described is a procedure for establishing a failure threshold for a pel (picture element) memory that provides high quality printing with less than 100% operability.

Printers for facsimile, word processing, and similar applications which produce prints from digital signals employ digital memories for storing print information as pels, sometimes called pixels. The simplest pel is stored as a binary digit, one value indicating white and the other, black. The pel density, usually measured in pels per inch, determines the resolution of the printed material. Very high resolution is obtained by 1000 pels/inch (1 million pels per square inch), but good quality printing is possible at lower densities, e.g., 2 0 pels/inch.

In word processing printers, the typeface designs (fonts) are stored as pels in a font memory. In response to a digitally coded character to be printed, an address is initially determined to access the beginning of the specified character block, and the address is incremented as the pels are retrieved and printed.

Even at the lower densities, a random incorrect pel in a character or picture area is not noticeable. Depending on the density and material being printed, several pels can be the wrong value without apparent adverse effects on the prints.

Acceptable good quality printing can be obtained using font memories containing cell failures. Memory technologies have not yet reached the stage of 100% yield of error-free memories. The majority of errors are single-cell failures. These are usually the result of microscopic...