Horizontal blank interrupt

Horizontal blank interrupt

A horizontal blank interrupt is a programming technique used in some systems, notably video games and consoles, to allow program code to be run in the periods when the display hardware is turned off, waiting for the TV to complete its horizontal blank, which takes about 10 μS.

The technique was only really useful before the entire display could be addressed directly with high speed CPUs attached to large frame buffers, that is, in the days of 8-bit systems. In this case the CPU was not terribly fast, and that 10 μS might be enough to run perhaps 40 to 60 instructions. That was enough to change a few registers in the display hardware however, which is why this technique was useful.

For instance, both the Bally Astrocade and Atari 8-bit family (originally intended to be a console) included HBI support. Both could display only four colors per pixel, but "which" four could be selected from a palette of 256, selected by storing the color number in one of four registers. By changing the values of the palette registers during the HBI, the system could select a new set of four colors on every line, leading to a number of "rainbow" displays with all 256 colors on screen (four per line).

ee also

*vertical blank interrupt
*parallax scrolling
*Raster interrupt


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Vertical blank interrupt — A vertical blank interrupt (or VBI) is a programming technique used in some systems, notably video games and consoles, to allow program code to be run in the periods when the display hardware is turned off, waiting for the TV to complete its… …   Wikipedia

  • Parallax scrolling — is a special scrolling technique in computer graphics, seen first in the 1982 arcade game Moon Patrol . In this pseudo 3D technique, background images move by the camera slower than foreground images, creating an illusion of depth in a 2D video… …   Wikipedia

  • Star Raiders — Infobox VG title = Star Raiders developer = Atari, Inc publisher = Atari, Inc designer = Doug Neubauer engine = released = 1979 genre = Space simulation modes = Single player ratings = platforms = Atari 8 bit family media = ROM cartridge… …   Wikipedia

  • Bally Astrocade — The Astrocade is an early video game console and simple computer system designed by a team at Midway, the videogame division of Bally. It was marketed only for a limited time before Bally decided to exit the market. The rights were later picked… …   Wikipedia

  • ANTIC — This article refers to the display chip. For the football manager, see Radomir Antić. For the magazine, see Antic (magazine). ANTIC ( Alpha Numeric Television Interface Circuit or Alpha Numeric Television Interface Controller ) is an early video… …   Wikipedia

  • Software-driven graphics modes for the Atari 8-bit computers — This article describes software driven graphics modes for the Atari 8 bit computers; that is, pseudo graphics modes whose capabilities are reliant on additional software rather than being supported directly in hardware.Any Point, Any ColorThe… …   Wikipedia

  • printing — /prin ting/, n. 1. the art, process, or business of producing books, newspapers, etc., by impression from movable types, plates, etc. 2. the act of a person or thing that prints. 3. words, symbols, etc., in printed form. 4. printed material. 5.… …   Universalium

  • Raster bar — Rasterbar redirects here. For the computing library libtorrent from Rasterbar see libtorrent (Rasterbar). Demoscene Concepts Demo Intro Demoparty Effects Demogroup Com …   Wikipedia

  • POSIX terminal interface — The POSIX terminal interface is the generalized abstraction, comprising both an Application Programming Interface for programs, and a set of behavioural expectations for users of a terminal, as defined by the POSIX standard and the Single Unix… …   Wikipedia

  • Color Graphics Adapter — The 640×200 2 color mode with its default foreground color Arachne Internet suite. The Color Graphics Adapter (CGA), originally also called the Color/Graphics Adapter or IBM Color/Graphics Monitor Adapter,[1] introduced in 1981, was IBM s first… …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.