Control circuit for a graphic machine and use of such a circuit in an interaction graphic machine

摘要

1. A control circuit for a graphic machine associated to a picture memory (1) in which the aspect of each picture spot is encoded by an aspect word having several bits, this circuit comprising - a colour transcoding table memory (4) containing colour words associated to a colour palette, this memory being addressed for read-out purposes by the picture memory (1) for each spot of the screen in a projection display device (6), the read-out of the picture memory (1) being performed synchronously with the scanning of the screen, - selection means allowing to transmit to the input of the table memory only a part of the aspect word bits, - a digital to analog conversion assembly (51, 52, 53) receiving colour words which have been read out from the transcoding table memory (4), and supplying analog control signals to the projection display device (6), characterized in that the number n of bits for encoding the aspect of the spots in the picture memory (1) exceeds the number n' of addressing bits for the table memory (4) and that the selection means (3) comprise - n' selector circuits (31, 32, ...38) located between the picture memory (1) and the table memory (4) and having each an input connected to the output of the picture memory (1) via an n-bits bus and a one-bit output as well as an n-bits control input, - a configuration control register (2), an output of which having n.n' bits is connected to the control inputs of the selector circuits and controls the latters in such a way that they select for each spot at each screen scan a subgroup comprising at most n, bits out of the n bits used to encode the aspect of the spot.