Video DAC



The NeoGeo uses a discrete video Digital-to-Analog Converter made of resistors and two 74LS273 latches which store the color value from the palette RAM while the pixel has to be displayed. This is controlled by either, or.





Each color component has its own set of 7 resistors. 6 of them are used with the actual color value (5 + 1 common bit). The last (SHADOW signal) is related to the and  registers (74HC259 latch).

The output voltage is then divided by 2200 / (6800 + 2200) = 4.1 (considered Voh of 74LS ?), to obtain a 1Vp-p max signal, which can be fed to the video encoder.