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Optimizing Throughput When Printing in Multiple Passes on a Serial Line Printer

IP.com Disclosure Number: IPCOM000034584D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Badani, HN: AUTHOR [+5]

Abstract

Disclosed is a method for minimizing the number of passes required to print a line. High speed serial line printers requiring multiple horizontal sweeps and multiple vertical passes to complete a single line of text are subject to severe throughput reduction when processing complex data streams. The method described below minimizes multiple vertical and horizontal sweeps by minimizing line-ending conditions. Serial line printers often must print different graphical elements at different speeds. An example of this would be a line that contains an APA (all-points addressable) image and letter quality text. Since the text may be printed at a different print resolution, hence a different speed, than the APA image, the printer requires two print passes to complete the line.

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Optimizing Throughput When Printing in Multiple Passes on a Serial Line Printer

Disclosed is a method for minimizing the number of passes required to print a line. High speed serial line printers requiring multiple horizontal sweeps and multiple vertical passes to complete a single line of text are subject to severe throughput reduction when processing complex data streams. The method described below minimizes multiple vertical and horizontal sweeps by minimizing line-ending conditions. Serial line printers often must print different graphical elements at different speeds. An example of this would be a line that contains an APA (all-points addressable) image and letter quality text. Since the text may be printed at a different print resolution, hence a different speed, than the APA image, the printer requires two print passes to complete the line. Another example is text that requires two different vertical passes, such as double high characters. Typically, the present print pass is interrupted when one of these events is encountered. This is often caused by print buffer limitations. If a buffer is created that can contain an entire line of text in the highest resolution, intelligent buffer processing can be performed. Commands from the PC or host are stored in a Host Buffer. The data in that buffer is processed in sequences of commands that cause either vertical paper movement, possibly multiple horizontal print passes, or paper-handling mode changes. Print pass sequences are processed until a termination condition (one that forces printing to occur) is reached. Line- terminating conditions are: 1. Commands that force vertical movement, such as

line feeds, vertical tabs, form feeds, etc.

2. Commands that require operator intervention, such

as font requests for which the font is not

available in the printer, stop requests from the

host, no data sent from the host for a specified

period of time, etc. A line image buffer that will contain the bit image data for an entire sequence is "opened" according to the mode of the first printable data in that sequence. The opening process consists of marking the buffer as being open, indicating how the data will be stored, storing all conditions that affect what will be printed (print mode, font, horizontal position, special mode states such as superscript or emphasize, etc.), and indicating which print pass is "active." For each sequence, indications as to what type of pass is required to complete the line, what type of passes have been completed, and what type of pass is "active" are kept. The sequence is then processed unt...