Browse Prior Art Database

CRT Display Feature Editing and Control

IP.com Disclosure Number: IPCOM000042100D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Stockwell, DA: AUTHOR

Abstract

Data display devices, particularly cathode ray tube (CRT) displays, usually have an associated display regeneration buffer in which coded representations of the characters to be displayed are stored. The display can be updated by addition, insertion or deletion of individual characters in the buffer or by rewriting portions or all of the buffer from a data source, such as a controller associated with an information handling system. However, such transactions with the controller may be necessary only to make such changes, refresh of the CRT image being made by repetitive readout from the buffer to the video circuitry of the CRT.

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CRT Display Feature Editing and Control

Data display devices, particularly cathode ray tube (CRT) displays, usually have an associated display regeneration buffer in which coded representations of the characters to be displayed are stored. The display can be updated by addition, insertion or deletion of individual characters in the buffer or by rewriting portions or all of the buffer from a data source, such as a controller associated with an information handling system. However, such transactions with the controller may be necessary only to make such changes, refresh of the CRT image being made by repetitive readout from the buffer to the video circuitry of the CRT. It is sometimes desired to provide additional bits of information associated with each of the characters in the display buffer denoting some characteristic to be applied to the character code read out from the buffer, such as color, highlighting (blinking, etc.) or selection of the decoding circuitry (character generator or generators) to be utilized in converting the character code to video. The extra bits may be provided in an optional extended buffer feature operable in synchronism with the main refresh buffer of the CRT. In any case, the transmission channel from the controller to the display may permit bytes of only a certain width (e.g., eight bits), and therefore it may not be practicable to load the refresh buffer and the extended buffer simultaneously. The arrangement described below provides controls whereby an extended attribute feature supervises loading or other modification of both the main or base refresh memory and its own associated extended attribute buffer (EAB). In Fig. 1, the controller 10 is connected via coaxial cable 12 to the display device 14 having the basic elements for the elementary aspects of the display, such as a CRT 16, and, as shown in Fig. 2, a refresh memory 18 for driving CRT 16 through intermediate digital-to-analog controls including a character generator, etc. (not shown). Fig. 1 shows an extended attribute (EAB) feature 20 which may be added to the base display 14 to further characterize the decoding and display of characters in the base display refresh memory 18, as aforedescribed. The base display 14 and the extended attribute feature 20 can be housed in the same cabinet, but are shown in Figs. 1 and 2 in a manner to emphasize their individual organizations and cooperation. The interface between 14 and 20 is shown in Fig. 1 to include a feature bus out FBO and an I/O-refresh counter bus from base display 14 to feature 20, and control lines (write base RAM, read base RAM, and step I/O ADR CTR) from feature 20, by which feature 20 and base 14 interact. Fig. 2 details the FBO interface between 14 and 20. Information flows via coax 12 between controller 10 and base 14. For example, a write command from controller 10 t...