CTIA and GTIA

GTIA ( Graphic Television Interface Adapter ) is the name of special chip ( custom chips ) of the 8 -bit home computer company Atari. He was, inter alia, installed in the equipment Atari 400, Atari 800, Atari 800 XL, Atari 600 and Atari 130 XL XE.

This is a special block of Atari. He takes over in the computers two important tasks. The first is to display the data generated by Antic on TV or monitor. To influence this representation, the GTIA contains a number of programmable registers with which, for example, the " actual appearance " of the colors can be determined, which purports to be the ANTIC. These colors are influenced by the television standard, so there are several versions for different television standards.

The second important task of the GTIA is the representation and management of the so-called Player-/Missile-Grafik. The ANTIC can display up to 4 players (players ) and up to 4 missiles ( bullets ) at the same time. In these " structures " are sprites, so to graphic elements that can be moved independently of the rest of the image across the screen. The GTIA took care of the movement of these elements, he determined whether a player / missile appeared before or after a certain part of the graphic image, and he is to determine collisions between players, missiles and the rest of the graph in the situation. This technique greatly relieved the processor when displaying moving graphics.

Other tasks of GTIA are querying the fire buttons of the joystick and some additional keys on the Atari keyboard, so the START, SELECT and OPTION keys. Finally, he is responsible also for generating the key clicks.