Talk:NTSC video: Difference between revisions
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(cursory examination of the PPU's video signal generator) |
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The part of the PPU that generates the video signal (immediately to the right of the NMI and CLK pins) appears to consist of a very long resistor between VCC and GND with taps at various points, and one of them (closest to VCC) is a switchable pulldown to GND (no doubt for color emphasis). The logic itself can select 12 different voltage levels (00/10/20/30, 0D/1D/2D/3D, synch, colorburst L/H, and GND), and they appear to correspond to 10 distinct voltage levels - one of the duplicates is at the highest voltage (likely 20/30), and the other one is the 3rd-lowest [non-GND] voltage (not sure which one). --[[User:Quietust|Quietust]] 17:59, 28 September 2011 (UTC) | The part of the PPU that generates the video signal (immediately to the right of the NMI and CLK pins) appears to consist of a very long resistor between VCC and GND with taps at various points, and one of them (closest to VCC) is a switchable pulldown to GND (no doubt for color emphasis). The logic itself can select 12 different voltage levels (00/10/20/30, 0D/1D/2D/3D, synch, colorburst L/H, and GND), and they appear to correspond to 10 distinct voltage levels - one of the duplicates is at the highest voltage (likely 20/30), and the other one is the 3rd-lowest [non-GND] voltage (not sure which one). --[[User:Quietust|Quietust]] 17:59, 28 September 2011 (UTC) | ||
*With the help of ChipSim, I've traced down exactly what the 12 voltage levels correspond to - Synch (GND), Colorburst L, Color 0D, Color xE/xF and Color 1D, Colorburst H, Color 2D, Color 00, Color 10, color 3D, Color 20 and Color 30 ("and" == two signals which select the same actual voltage). --[[User:Quietust|Quietust]] 11:17, 29 October 2012 (MDT) | |||
Revision as of 17:17, 29 October 2012
The part of the PPU that generates the video signal (immediately to the right of the NMI and CLK pins) appears to consist of a very long resistor between VCC and GND with taps at various points, and one of them (closest to VCC) is a switchable pulldown to GND (no doubt for color emphasis). The logic itself can select 12 different voltage levels (00/10/20/30, 0D/1D/2D/3D, synch, colorburst L/H, and GND), and they appear to correspond to 10 distinct voltage levels - one of the duplicates is at the highest voltage (likely 20/30), and the other one is the 3rd-lowest [non-GND] voltage (not sure which one). --Quietust 17:59, 28 September 2011 (UTC)
- With the help of ChipSim, I've traced down exactly what the 12 voltage levels correspond to - Synch (GND), Colorburst L, Color 0D, Color xE/xF and Color 1D, Colorburst H, Color 2D, Color 00, Color 10, color 3D, Color 20 and Color 30 ("and" == two signals which select the same actual voltage). --Quietust 11:17, 29 October 2012 (MDT)
