Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Address Translation for Video Display Image Composition

IP.com Disclosure Number: IPCOM000099839D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 4 page(s) / 133K

Publishing Venue

IBM

Related People

Bealkowski, R: AUTHOR [+2]

Abstract

A technique is described whereby address translation is provided for video display composition, as used in personal computers, through the use of an address translation random-access memory (TRAM) mechanism. The TRAM provides programming flexibility by eliminating the need to move data in and out of the video memory buffer every time a change of windowed information occurs.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Address Translation for Video Display Image Composition

       A technique is described whereby address translation is
provided for video display composition, as used in personal
computers, through the use of an address translation random-access
memory (TRAM) mechanism.  The TRAM provides programming flexibility
by eliminating the need to move data in and out of the video memory
buffer every time a change of windowed information occurs.

      Data for a video image is typically stored sequentially in a
video memory buffer.  To update the video image, data must be
manipulated within the video buffer.  The concept described herein
provides a mechanism which allows the display video image to be
dynamically composed without the need to move data within the video
buffer.

      Generally, the personal computer character mode display image
is eighty characters wide by twenty-five vertical rows.  Each
character is defined as a word value in video memory, where each word
is defined by a character/attribute pair.  The character byte is the
ASCII value for the character to be displayed.  The attribute byte is
used to define the color values to be used when displaying a
character.

      Each character/attribute word is stored in the video memory
buffer in sequential order.  The first character position on the
screen is at word location zero, the second character position is at
one, the first character of the second row is at word location
eighty, etc.  Therefore, the first row is word location 0-79, the
second 80-159, the third 160-239, etc.

      To change which character is to be displayed in a position on
the screen, the data stored in the corresponding location in the
video buffer must be changed.  When windows within the displayed
screen are to be updated, a substantial amount of data must be moved.

      This moving of data is avoided by adding an indirect addressing
mechanism to the hardware to control the access to the video memory.
The mechanism, called the "Translation RAM" (TRAM), allows each
displayed position to be defined from any location within the video
memory buffer.  The TRAM assists in redefining the order in which
stored video information is to be displayed by providing assistance
to the programmer in developing applications, such as window
managers.

      A program requiring the display of a number of windows on a
screen must move data from separate buffers into the displayable
area.  The movement of this data composes the screen and is shown to
the user, such as the display shown in Fig. 1.

      Typically, the total amount of video memory available for
character sto...