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Memory Allocation and Deallocation for Print Data in APA Printers

IP.com Disclosure Number: IPCOM000034622D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 86K

Publishing Venue

IBM

Related People

Czyszczewski, JS: AUTHOR [+3]

Abstract

A method is described for effectively using memory and DMA to format and print data in high density APA (all-points-addressable) printers. Large amounts of memory are needed to store data; for example, one square inch of data in a 240 x 360 pel/inch resolution requires over 10,000 bytes of memory. Therefore, it is impractical to store an entire page of text, because the cost of adequate memory chips would be prohibitive, especially for low cost letter quality printers. This requires that the print data be formatted and "rasterized" (converted into dot patterns) in sections in RAM while printing is in progress. This method is intended for use on an R2T2 (Resistive Ribbon Thermal Transfer) technology printer , but the ideas presented here can be extended to a wide variety of print technologies.

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Memory Allocation and Deallocation for Print Data in APA Printers

A method is described for effectively using memory and DMA to format and print data in high density APA (all-points-addressable) printers. Large amounts of memory are needed to store data; for example, one square inch of data in a 240 x 360 pel/inch resolution requires over 10,000 bytes of memory. Therefore, it is impractical to store an entire page of text, because the cost of adequate memory chips would be prohibitive, especially for low cost letter quality printers. This requires that the print data be formatted and "rasterized" (converted into dot patterns) in sections in RAM while printing is in progress. This method is intended for use on an R2T2 (Resistive Ribbon Thermal Transfer) technology printer , but the ideas presented here can be extended to a wide variety of print technologies. For ease of explanation of the method, the R2T2 application will be used. With this particular printer, the print head was 120 pels high, and could print 1/2 inch of text with each pass (approximately three lines). It could also print graphics and image data. The print tasks were delimited by print controls such as line feed, carriage return, form feed and were also separated by resolution. Print tasks were also received in any order, one page at a time.

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In order to maximize raster speed and average workload so the print head could maintain a constant print speed for each pass, data was rasterized in blocks, on the order of two inches in length and 1/2 inch in height (the height of the print head). Characters that span the block boundary are rasterized in an "overflow" region that is part of the next swath block (Fig. 1). As the blocks and overflow regions are completed, they are released to the print mechanism, and commands containing positional data are sent with the block to indicate the location of the s...