2 replies to this topic

[doppel]

So the NTSC frame timing is well known, but I can't seem to find any information concerning PAL timing. Obviously, the frames are longer than in NTSC (50 scanlines longer, if 312 is the correct number), but other timing information seems obscure. Does anybody know the timing the PAL 7800 MARIA used (when VBLANK starts, when it ends, how much screen display is visible, how long DMA runs)?

[doppel]

doppel, on Thu Jul 22, 2010 2:03 PM, said:

So the NTSC frame timing is well known, but I can't seem to find any information concerning PAL timing. Obviously, the frames are longer than in NTSC (50 scanlines longer, if 312 is the correct number), but other timing information seems obscure. Does anybody know the timing the PAL 7800 MARIA used (when VBLANK starts, when it ends, how much screen display is visible, how long DMA runs)?

Whoops, I totally forgot this document even existed (it isn't linked to by most of the other 7800-related pages). So I guess I didn't really need to start a new thread, so, moderators, feel free to do whatever to this.

http://www.atari7800...Maria_Specs.pdf

[nichtsnutz]

Hello all,

this is my first post here although I read atariage for two years now,so I first would like to thank the people behind this nice forum and also those who contributed so much to the 8 bit atari systems.In my profile I have written a little about my interests,so read there if you like.
Ok,now to topic.
I am primary interested in the hardware of the ataris and I have taken some timings of the
PAL MARIA sync and blank signals.What the documentation states is right (454 Clocks per line and 313 lines per frame for PAL).Although I am a bit confused,because 454 Clocks / 4 = 113.5 cpu clocks per line,so at least on PAL there is no integer cpu clocks per line when I assume thar the cpu runs with 1.77MHz.(No switch to the slow mode)
Anyway,if someone is interesed I have also attached the Logicport files,you can open them with their software to measure things.

Bye,
Vassilis

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