high resolution colour graphics card (part 2) - the second in a series of articles describing a 512x512 or 512x256 pixel, black 8- white or colour, graphics card

high-resolution colour graphics card - 2 by P Lavigne Et D Meyer A graphics display processor (GDP) such as the Thomson Types EF9365, EF9366, or EF9367 is designed to generate the video signal and the sync(hronization) signals. To the user, it acts as an intelligent graphics screen controller with a picture scan that can be programmed via an eight-bit microprocessor. Apart from these func- tions, it also contains circuits for writing to the screen memory: a vector generator and a character generator. These enable writing on the screen at high speed (for instance, a 512 pixel diagonal in less than 7001.40 so that the host microprocessor is relieved of these basic tasks. The GDP has virtually no effect on the memory addressable by the micropro- cessor since it occupies only sixteen addresses: with the addition of external registers such as scroll, colour, and page switching, to no more than twenty ad- dresses. A further advantage is that the host and GDP memories have completely dif...