Difference between revisions of "Video DAC"

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[[File:mvs_viddac.jpg|right|thumb|Resistor array forming the video DAC on a 1FZS MVS board.]]
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[[File:mvs_viddac.jpg|right|thumb|Resistor array forming the video DAC on a 1FZS.]]
  
The NeoGeo video DAC was made by using digital latches and precision resistors.
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The NeoGeo uses a discrete video DAC made of precision resistors, and two 74LS273 latches controlled by [[NEO-B1]], [[NEO-GRC]] or [[NEO-GRZ]].
  
TODO: Resistor values, schematic ?, "[[Dark bit]]"...
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[[File:aes_viddac.png|right|thumb|Video DAC on a AES board.]]
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[[File:aes_viddac_schematic.png]]
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Each color component has its own set of 7 resistors. 6 of them are used with the actual color value stored in the [[palette RAM]] (5 + 1 [[Palettes#Dark bit|common bit]]). The last (SHADOW signal) is related to the REG_DISPDISABLE and REG_DISPENABLE registers (74HC259 latch).
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The output voltage is then divided by 5 to obtain a 1Vp-p max signal, which can be fed to the [[CXA1145]] encoder.
  
 
[[Category:Chips]]
 
[[Category:Chips]]
 
[[Category:Video system]]
 
[[Category:Video system]]

Revision as of 13:17, 8 February 2011

Resistor array forming the video DAC on a 1FZS.

The NeoGeo uses a discrete video DAC made of precision resistors, and two 74LS273 latches controlled by NEO-B1, NEO-GRC or NEO-GRZ.

Video DAC on a AES board.

Aes viddac schematic.png

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

The output voltage is then divided by 5 to obtain a 1Vp-p max signal, which can be fed to the CXA1145 encoder.