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Underscoring With Multiple Thickness Capability As a Function of Scan Direction and Print Orientation

IP.com Disclosure Number: IPCOM000039802D
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 6 page(s) / 61K

Publishing Venue

IBM

Related People

Hanna, SD: AUTHOR [+2]

Abstract

This article describes an underscoring feature of a baseline character generator that can be used to generate a raster image of a page from a memory that contains a coded and ordered representation of the page. The design implements underscoring on a baseline character gener ator which prints in 8 scan directions, and has the ability to print variable height and width characters. The design allows underscore (and/or double underscore) to be associated with each character regardless of which of the 8 print scan orientations are being used. Underscore is considered in two different printing modes: normal and rotated. A normal underscore is an underscore which is perpendicular to the scan direction while a rotated underscore is parallel to, or in the, scan direction.

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Underscoring With Multiple Thickness Capability As a Function of Scan Direction and Print Orientation

This article describes an underscoring feature of a baseline character generator that can be used to generate a raster image of a page from a memory that contains a coded and ordered representation of the page. The design implements underscoring on a baseline character gener ator which prints in 8 scan directions, and has the ability to print variable height and width characters. The design allows underscore (and/or double underscore) to be associated with each character regardless of which of the 8 print scan orientations are being used. Underscore is considered in two different printing modes: normal and rotated. A normal underscore is an underscore which is perpendicular to the scan direction while a rotated underscore is parallel to, or in the, scan direction. These two types of underscore are controlled by the same logic pipeline but are implemented as pels in two separate sections of the logic. Normal underscore is always put at the bottom of the first font fetch of a character regardless of which of the 4 normal scan modes is in use. This underscore is turned into pels in the font data aligner chip. Rotated underscore is forced into different locations within the character box depending on which of the 4 rotated scan modes is in use. Pels are generated on the font data aligner chip in a different way than the normal underscore, and timing for the rotated underscore is generated on a different chip. A signal named "black*" is the control for blacking out a fetch of font data to cause rotated underscore. The following is an overview of the character generator operation. The character generator consists of 4 memories which are addressable by the control unit: Font

Address and Escapement (A/E) Page Buffer (PB)

Column Position and Escapement (CPE) Font Memory The font memory contains the raster dot (pel) patterns of all printable characters with one bit of storage for each dot or pel. A logical "1" appears as a dark pel. The control unit can read and write this memory as halfwords (16 bits) or as bytes. Address and Escapement Memory The address and escapement memory is a pointer table consisting of one entry for every character code (256) of every font (16) that can be printed. Each entry specifies the size of the character (height and width) and the address in the font where the character starts. There are two sets of these tables (normal and rotated), so there are a total of 8K (8192) entries (32K bytes). Only 254 character codes can be printed per font if 2 system codes are used as an end of line (EOL) and an end-of-print (EOP) character. (This is assuming an EOL and EOP code is in each font, which is not necessary from a hardware point of view.) Each entry is a full word (32 bits) addressable from the processor as two 16-bit halfwords or as four 3-bit bytes, and consists of the starting address of the character (font referen...