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Browse Prior Art Database

Invertible Display

IP.com Disclosure Number: IPCOM000120091D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 84K

Publishing Venue

IBM

Related People

Sekiya, K: AUTHOR

Abstract

Disclosed is a systematic method for turning computer screen images upside down without affecting the software running on them. It does so by inserting a glue circuit between a bitmap frame buffer and its display controller, which converts the buffer addresses and the order of data bits to the inverted position and does not affect the function of the display controller.

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

Invertible Display

      Disclosed is a systematic method for turning computer
screen images upside down without affecting the software running on
them.   It does so by inserting a glue circuit between a bitmap frame
buffer and its display controller, which converts the buffer
addresses and the order of data bits to the inverted position and
does not affect the function of the display controller.

      Hereafter, 'inversion' means 'turning upside down' and liquid
crystal display (LCD) refers to common kinds of flat panel display
device.

      The object display subsystem for this method has a bitmap frame
buffer and a display controller, as shown in Fig. 1.  The cathode ray
tube controller (CRTC) controls the display, and there are two
logical access paths to the bitmap frame buffer. The host system
generates a screen image on the bitmap buffer through the Host
Read/Write (Host R/W) path and the CRTC reads the image through the
CRTC Read (CRTC R) path and shows it on a display.

      Fig. 2 shows a simple screen and an example of inversion.
Suppose the frame buffer has a depth of 1 bit, the real buffer
address of the top left of the screen is 0000, that of the bottom
right is AAAA, and the bit order of the data is 0 to 7 from
left to right.  Actually, each bit of the data '01010011' and
'11001010' should be shown as on/off brightness.  In this example,
the host system intends to generate a bit image of '01010011' in the
top left corner of the screen but the actual image appears at the
bottom right corner of the display in reversed order of bits.

      One method of implementation is to insert a glue circuit into
the CRTC R path.  When the subsystem is in inversion mode, the
circuit converts the CRTC's Read address XXXX to AAAA - XXXX
(subtractio...