I don't know why we keep getting these stupid arguments, but I figured out a way to prove it, trivially reproduced by anyone else with a TV with an S-video jack.
I wrote a simple program that will bit-bang a replacement luma signal using the DMC DAC. We can then use the NES's normal video signal as chroma, and we can skew the two so that the colorburst is on screen.
A simple pattern (a giant letter I with top and bottom bars) will let us do a few other tests.
Additionally, for anyone who wants to see what will happen if the color chosen is not phase 8, pressing certain key combinations on controller one when you release reset will choose other colors instead of $08 for the background.
If you power on holding:
Sel+Up=$01 Sel+Dn=$02 Sel+Lt=$03 Sel+Rt=$04
St+Up=$05 St+Dn=$06 St+Lt=$07 St+Rt=$08
Up=$09 Dn=$0A Lt=$0B Rt=$0C
Start=$18 Select=$28 St+Sel=$38
the backdrop will be the specified color. Then release all buttons to begin.
After bit-banging RS170 has started, you can use up/down/left/right to move the relative phase of the fake S-video luma relative to the 2C02-as-chroma. A and B will change the color for the backdrop.
Source:
Many thanks to Nintendulator's pixel counters, which made this about 10 times faster and less painful than it would have been otherwise.
This should be easily adapted to the Dendy to test there, and painfully adapted for the 2A07.
I wrote a simple program that will bit-bang a replacement luma signal using the DMC DAC. We can then use the NES's normal video signal as chroma, and we can skew the two so that the colorburst is on screen.
A simple pattern (a giant letter I with top and bottom bars) will let us do a few other tests.
Attachment:
Additionally, for anyone who wants to see what will happen if the color chosen is not phase 8, pressing certain key combinations on controller one when you release reset will choose other colors instead of $08 for the background.
If you power on holding:
Sel+Up=$01 Sel+Dn=$02 Sel+Lt=$03 Sel+Rt=$04
St+Up=$05 St+Dn=$06 St+Lt=$07 St+Rt=$08
Up=$09 Dn=$0A Lt=$0B Rt=$0C
Start=$18 Select=$28 St+Sel=$38
the backdrop will be the specified color. Then release all buttons to begin.
After bit-banging RS170 has started, you can use up/down/left/right to move the relative phase of the fake S-video luma relative to the 2C02-as-chroma. A and B will change the color for the backdrop.
Source:
Attachment:
File comment: (WTFPL/CC0; requires ca65)
colorburst-phase-demonstration.zip [6.5 KiB]
Downloaded 165 times
colorburst-phase-demonstration.zip [6.5 KiB]
Downloaded 165 times
Many thanks to Nintendulator's pixel counters, which made this about 10 times faster and less painful than it would have been otherwise.
This should be easily adapted to the Dendy to test there, and painfully adapted for the 2A07.