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De0 vga dac help

Honored Contributor II



I am trying to produce a vga output to my crt. I understood the basics of timing but DE0 board's 4 bit resistor network dac confuses me. I searched over internet but I couldn't find anything helpfull. How should I use it? For example what will vga red signal "1111" produce?  


On manual it says to look for ADV7123 dac datasheet. How is DE0 related with ADV7123? Is there a secret dac like this on DE0 board that is not showed on schematics? 


I am really confused any help will be greatly appreciated. 



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Honored Contributor II

I think I figured it out the DE0 board has nothing to do with ADV7123 DAC. I don't know why it is showed as a reference in manual. My experiments showed that four bit resistor network simply produce different voltage levels for each rgb signal. For example with vga_R3 pin as MSB, "0000" red signal will produce blank and "1111" red signal will produce the brightest red pattern. So each 4 bit resistor network helps the user to produce 16 different tones of a color. 


I just have figured out that from experiments so I have to study more about this multiple bit color subject. Please share any references that you know about this subject.