9 Color Luminance Registers

A. Description

There are four registers (shown in figure 3) that contain color-lum codes. Four bits of color code and three its of luminance code may be written into each of these registers (COLUP0, COLUP1, COLUPF, COLUBK) by the microprocessor at any time. These codes (representing 16 color values and 8 luminance values) are given in the Detailed Address List.

B. Multiplexing

The serial graphics output from all six objects is examined by the priority encoder which activates one of the four select lines into a 4 x 7 multiplexer. This multiplexer (shown in figure 3) then selects one of the four color-lum registers as a 7 line output. Three of these lines are binary coded luminosity and go directly to chip output pads. The other four lines go to the color phase shifter.

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