AV output ntsc/pal

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KanedaFr
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AV output ntsc/pal

Post by KanedaFr » Fri Aug 06, 2010 1:02 pm

I was about to mod my genny to RCA stereo output to be able to video capture when I found this interesting post.
Can you confirm me a PAL megadrive 1 with a multi region switch won't output a NTSC RCA valid signal w/o this mod ?

HardWareMan
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Post by HardWareMan » Sat Aug 07, 2010 5:23 am

Yes. I confirm that. I've done this at early 90's. More over: MD clones have place for quarz resonator and capacitor. Basic PAL/NTSC coder from SONY CXA1145 has both modes: PAL and NTSC. But it take color carrier from VDP, wich valid for NTSC only with 53.634165MHz MCLK and for PAL with 52.203424MHz. So, if you switch NTSC console to PAL mode or PAL console to NTSC mode VDP will output wrong color carrier. So, if you isolate PAL/NTSC coder with its own color carrier generator (by setup 4.43MHz resonator) and PAL/NTSC switch (wich connect to pin 46 VDP) you will get valid color signals.
But there some "features":
1. You will get 4.43MHz PAL and 4.43MHz NTSC (it's legal for most TV's). To solve this, you must use 2 quarz resonators or 2 MCLK generators.
2. You will get PAL60 on NTSC console (it's legal for most TV's). To solve this, only 2 MCLK generators required.

And, you can isolate VDP PAL/NTSC pin from IO chip and get PAL/NTSC hardware modes independ of region register (wich control by pins 25 and 26 315-5309). So, you can run your region cartriges on foreign FPS and get MegaKey for free. :3

TmEE co.(TM)
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Post by TmEE co.(TM) » Mon Aug 09, 2010 6:47 am

Too bad MD2 does not have 50/60 and region signals separate :(
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notaz
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Post by notaz » Mon Aug 09, 2010 2:01 pm

HardWareMan wrote:But it take color carrier from VDP, wich valid for NTSC only with 53.634165MHz MCLK
53634165? All sources I've seen so far list 53693100, for example this image:
http://interbutt.com/postimages/genesis1_pcb.jpg

KanedaFr
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Post by KanedaFr » Mon Aug 09, 2010 3:07 pm

apart from sound, would it be easier to replace it with a CXA1645P ?

HardWareMan
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Post by HardWareMan » Tue Aug 10, 2010 3:14 am

notaz wrote:
HardWareMan wrote:But it take color carrier from VDP, wich valid for NTSC only with 53.634165MHz MCLK
53634165? All sources I've seen so far list 53693100, for example this image:
http://interbutt.com/postimages/genesis1_pcb.jpg
Ah. Yes, my mistake.

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