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debugger

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Posts posted by debugger

  5. Posted

    What i want to say, is: does the 7800 have a fixed color palette? Like "color 1 is black, color 2 is red" etc, a color number that's later retrieved by the vdp from palette ram to paint the color in the tv (i bet that's not the way, because there isn't any place in the memory map) or a 8 bit value composed with a few bits for the color, like (for example!) 3 bits for red, 3 for green and 2 for blue? Any help would be very appreciated! :)

  6. Posted

    I see in the Maria register list this info:

     

    0020 - Background color

    0021 - Palette 0 color 1

    0022 - Palette 0 color 2

    0023 - Palette 0 color 3

    0025 - Palette 1 color 1

    0026 - Palette 1 color 2

    0027 - Palette 1 color 3

     

    (etc)

     

    What values do i have to store in those registers? I mean, what color format does the 7800 use? If i want a blue or a red, how do i specify it? Thanks :)

  11. Posted

    Sorry for always asking about programming stuff guys :)

    I'm reading the 7800 bios disassembly and i'm surprised about this:

     

    STA LF112

     

    LF112 label is not defined in any place of the code or am i becoming crazy of reading too much 6502 asm lately? Did anyone tried to assemble again this file? :)

  16. Posted

    Hello guys :) I have another question to you. After downloading some Atari 7800 games i noticed something that i don't understand. First bytes of the roms (raw .bin dumps, or after the 128 bytes of the A78 header) there are bytes that can't be 6502 code. For example, Xenophobe NTSC contains a lot of AA bytes, Asteroids NTSC a repeating pattern 03 FC 00, or Ace of Aces, that even contains a lot of ascii code! What i'm missing here? I tought the game code started in the first byte of the rom!

     

    Thaaaaanks a lot for your help :)

  22. Posted

    Well, for 3 reasons:

     

    1: Because i'm not sure if i can play NTSC games on my PAL console, but in case i can, i'll play slower (at 50hz) and with black borders at top and bottom of the screen (because increased screen resolution in PAL).

     

    2: Because the Atari 7800 was designed to be NTSC :)

     

    3: Because if PAL games don't work on NTSC systems, maybe i can play the PAL versions i have but with correct resolution/speed :)

     

    Debugger

  23. Posted

    Erm... guys what reply speed is this? :)

     

    Mm nice to see the modification is suited for ntsc systems too, those are good news (and bad too because i'll have to buy two consoles, then) 8)

     

    By some reason or other i tought the upload worked in another way, maybe because the ones i use at work (not for atari, of course) work in a completely different way.

     

    The reason to wanting to convert a PAL 7800 into NTSC is that i have more than one PAL consoles, but 0 NTSC ones :)

     

    Thanks for the ultra fast responses.. :)

  24. Posted

    Hi all :)

     

    I'm just curious about a text file i readed somewhere, about converting a PAL Atari 7800 into a homebrew dev system. Considering that (afaik) the bigger base of Atari 7800 users have a NTSC system, why is this modification suited only for PAL consoles?

     

    And why anyone would like to put an EPROM instead of the original console BIOS? :?

     

    And the last question.... I don't have any NTSC 7800, mine is PAL, but i love NTSC :) I would like to convert one of my consoles to NTSC but i haven't found any information about this, maybe it's not possible? :)

     

    Sorry for not pasting the URL, but i can't remember where i dowloaded the file :P

     

    Debugger

  25. Posted

    Ok, thanks for all the responses, i think i know now all what i need to continue :) The only thing i don't fully understand is this stack/tia registers overlap, because it's fun to write to the registers pushing values, but this means that when i need to push something into the stack the console will become crazy, right? :)

     

    Eckhard: The secret project is a secret thing :) I don't like vaporware at all, so i preffer to work on this before i tell anything to anyone because for now it does not work at all and i don't even know if i'll be able to do it ;)

     

    Btw, i have another question, but as it's a totally different thing i'll make another thread for it :)

     

    Debugger

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