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  1. #1
    EmuTalk Member albertwesker's Avatar
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    Sega Master System

    i don't know of any other good forums for general emu development, so i wanted to start a thread on SMS emu dev here. ^_^

    anyway, here's an excellent resource for sega master system documentation: http://www.smspower.org/dev/docs/

    if anyone has had a go at this system, post your experience here! i'd be glad to hear about it. also, please post any tech documents you know of that you don't see listed in that link!



    maybe a mod can sticky this thread as well?

  2. #2
    A lowdown dirty shame blueshogun96's Avatar
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    Quote Originally Posted by albertwesker
    i don't know of any other good forums for general emu development, so i wanted to start a thread on SMS emu dev here. ^_^

    anyway, here's an excellent resource for sega master system documentation: http://www.smspower.org/dev/docs/

    if anyone has had a go at this system, post your experience here! i'd be glad to hear about it. also, please post any tech documents you know of that you don't see listed in that link!
    That's cool. I never even thought of even touching sega master system. I'll give it a look, and maybe you'll get some good responses.
    maybe a mod can sticky this thread as well?
    dunno, a thread has a better chance of being a stiky depending on the interest of the members (as well as mods/admins) in emulation of this console. I tried to get an interest in atari 2600 going, but no luck here. Oh well, at least I found the documentation I was looking for ( even though a google search took F-O-R-E-V-E-R).

  3. #3
    Emulator Developer ShizZy's Avatar
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    If it becomes a useful resource I'm sure it'll be stickied in time. I never though of doing a SMS emu, maybe when I finish my other ones first.
    ~****Zy

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    Gekko GameCube Emulator

  4. #4
    Moderator aprentice's Avatar
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    Quote Originally Posted by ****Zie
    If it becomes a useful resource I'm sure it'll be stickied in time. I never though of doing a SMS emu, maybe when I finish my other ones first.
    I've "looked" into it, as in i've emulated the complete memory system including paging, and used the z80 from my gameboy emu, spent a total of 2 days on it but then put it on freeze because I just didn't have the time and still don't really, the sms doesn't look that bad, but thats not code for its easy, its definately easier than the nes

  5. #5
    EmuTalk Member
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    You think NES is harder than PSX? I'm thinking one of the best parts about the PSX is that there's no extra hardware to emulate. You don't need to find documentation on all kinds of different mappers .

  6. #6
    PCSX2 Coder refraction's Avatar
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    Quote Originally Posted by bcrew1375
    You think NES is harder than PSX? I'm thinking one of the best parts about the PSX is that there's no extra hardware to emulate. You don't need to find documentation on all kinds of different mappers .

    well having seen people work on PSX and worked on PS2 emulation myself, i can tell you now, PSX is a **** load harder than NES ;p

  7. #7
    A lowdown dirty shame blueshogun96's Avatar
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    Quote Originally Posted by refraction
    well having seen people work on PSX and worked on PS2 emulation myself, i can tell you now, PSX is a **** load harder than NES ;p
    Yeah, emulation of a 6507 vs a MIPS in difficulty? No brainer.

  8. #8
    EmuTalk Member albertwesker's Avatar
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    ok, so a slight delay and now i'm beginning. i've been pouring over the docs the past few days and one thing in particular is bothering me. maybe some of you with z80 exp can shed some light on this. here are two exerpts from the zilog z80 user manual:

    "There are also two sets of accumulator and flag registers and six special-purpose registers."

    "The CPU includes two independent 8-bit accumulators and associated 8-
    bit flag registers. The accumulator holds the results of 8-bit arithmetic or
    logical operations while the FLAG register indicates specific conditions
    for 8-bit or 1 16-bit operations, such as indicating whether or not the
    result of an operation is equal to zero. The programmer selects the
    accumulator and flag pair with a single exchange instruction so that it is
    possible to work with either pair."

    i understand what the accumulator and flags are for but what i'm having trouble understanding is why there is a 'pair' of them and when to use one or the other. anyone care to expound on these two details?

  9. #9
    EmuTalk Member TJA's Avatar
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    It is quite simple actually all the z80 registers can be accessed as a pair making a 16-bit register or as an 8-bit single registers, for example the accumulator register is register A, this register is paired with the flag register F making the register AF, you can use unsigned char (e.g. unsigned char reg_A ) to emulate a single register and int for a pair ( e.g. int reg_AF ) but if you do it this way make sure the values in the paired and single register are the same after each cpu execution for example the first 8-bit of the reg_AF>>8 should be equal to the 8-bit value in reg_A, as for the flag register reg_F I found for simplicity sake to just use four integer values e.g. int carry_flag, int zero_flag etc to hold its values rather than having to deal with accessing individual bits of reg_F, it just makes your code easier to follow i think.

    Cheers, TJA.

    As for when a pair or single is used that just depends on the instruction you are emulating.
    Last edited by TJA; November 20th, 2005 at 16:45.
    Visit my webpage for all the tips, tutorials, systems info, cpu instution set docs etc you will need for Emulation Programming, and General Programming.

    HowToEmulation

  10. #10
    Emulator Developer ShizZy's Avatar
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    Yes, like TJA said, the reason for the individual registers and pairs is just for simplicity with the instructions. If you wanted, you could just use 16bit pairs, then mask out just the 8bit parts when they are refferenced, or vice versa, but that could get sloppy. And rather than making sure they are all the same after each instruction, just set them up as a union structure.
    ~****Zy

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