Atari GTIA
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The Graphic Television Interface Adapter ( GTIA ) and its predecessor, the Color Television Interface Adapter ( CTIA ), are special electronic components from the US manufacturer Atari that perform various tasks, mainly in the field of image generation . They were developed in different versions for the television standards NTSC , PAL and SECAM and can be found in the home computers Atari 400 (CTIA, from 1982 GTIA), Atari 800 (CTIA, from 1982 GTIA), the models of the XL and XE series as well in the Atari 5200 game console .
Working method
After the ANTIC microprocessor has processed the graphic data for the current pixel (image point block), the GTIA adds user-definable components in the second step - before outputting, for example, on the television. This includes coloring with the help of a palette of 16 colors in 16 brightnesses each and the integration of image data from a maximum of eight independent but each monochrome graphic objects, the sprites . While these objects, also known as “players” and “missiles” in Atari jargon, are copied into the background image according to user-definable overlapping rules, a collision check is carried out at the same time . It is determined whether the sprites touch one another or certain parts of the background image (“playfield”) on the currently processed pixel block. These abilities were developed - as already indicated by the names "Playfield", "Player" and "Missiles" - for the simplified creation of games with interacting graphic objects and fast game play. In the last work step, the actual video signal is generated from the merged graphic data of the currently processed pixel and fed into the RF modulator for output on the connected television. The procedure beginning with the ANTIC preprocessing is then repeated for the next block of pixels until the entire picture is displayed on the television. In addition, the module takes on other tasks such as querying the joysticks and some special buttons.
literature
- Julian Reschke, Andreas Wiethoff: The Atari professional book. Sybex-Verlag GmbH, Düsseldorf, 1986, ISBN 3-88745-605-X
- Eichler, Grohmann: Atari 600XL / 800XL Intern. Data Becker GmbH, 1984, ISBN 3-89011-053-3
Web links
Notes and individual references
- ↑ Julian Reschke, Andreas Wiethoff: The Atari professional book. Sybex Verlag, 2nd edition 1986, pp. 201-214.