Browse Prior Art Database

All Points Addressable Raster Scan Graphics for Cathode Ray Tube with Dual Ported Bit Map

IP.com Disclosure Number: IPCOM000051299D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 3 page(s) / 78K

Publishing Venue

IBM

Related People

Kummer, DA: AUTHOR [+2]

Abstract

The system shown in Fig. 1 provides an all-points-addressable graphic capability, together with alphanumeric capability, using the timing signals from an existing raster scan cathode ray tube (CRT) adapter. The CRT adapter generates graphical information for defining alpha numerical characters. In addition, the CRT adapter also generates horizontal, vertical and clock signals, which are applied to the CRT to control the image thereon.

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All Points Addressable Raster Scan Graphics for Cathode Ray Tube with Dual Ported Bit Map

The system shown in Fig. 1 provides an all-points-addressable graphic capability, together with alphanumeric capability, using the timing signals from an existing raster scan cathode ray tube (CRT) adapter. The CRT adapter generates graphical information for defining alpha numerical characters. In addition, the CRT adapter also generates horizontal, vertical and clock signals, which are applied to the CRT to control the image thereon.

Referring to Fig. 1, the main central processing unit (CPU) 10 provides signals to a data bus and an address bus, and receives data signals on the data bus. CPU 10 has associated therewith a main storage 12 which is addressable by the signals on the address bus to store the data on the data bus or provide data to the data bus. CRT adapter 14 is a conventional module which may be used in conjunction with CPU 10 to provide timing signals, such as the vertical, horizontal and clock signals, to CRT 16 and alphanumeric data signals to OR gate 18 to cause alphanumeric characters to be displayed on CRT 16.

The graphics unit 20, shown in the dashed lines, includes a graphics control unit 22 which is driven by the vertical, horizontal and clock timing signals from CRT adapter 14. The graphics storage, or bit map, 24 is used as part of the main storage or as an extension of the main storage. All bytes in graphics storage 24 are directly addressable by CPU 10 at any time. If desired, the graphics storage 24 may be used as general-purpose storage by disabling the graphics information from appearing on the CRT 16 by including AND gate 34. Thus, the added cost of the graphics storage 24 is offset by also using it as general-purpose storage when the graphics feature is not being used.

Graphics information and alphanumeric characters provided from CRT adapter 14 are allowed to co-exist throughout the entire CRT 16 screen. This provides an easy manner for labeling graphics or plots. Graphics control unit 22 provides the control and addressing of graphics storage 24 when non- alphanumeric data is displayed. It also determines whether CPU 10 will have an access to graphics storage 24 through direction control 26 and selector 28 or whether the storage cycle will be used to display graphical information in the fetched byte. Direction control 26 and selector 28 are under...