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Thread: [GUIDE] Make a Reprogrammable Genesis Cart

  1. #151
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    Quote Originally Posted by wal666 View Post
    An observation and a question here,
    It seems the music is stored on the bottom ROM. I forgot to put the top ROM in and I got music and no video haha!
    I used 2 27c160 eproms because that's all I had and this works!
    I tried to make the image region free but wrecked it every time so I must be doing something wrong.
    I entered JUE in the correct spot but how do I check checksum?
    Great, so it works 100%?

    I use uCON64 to fix checksums, but this looks like a simpler program:
    http://segaretro.org/ESE_FixCheckSum

    My guess is that the graphics are stored in the upper ROM and when the console enables it, the internal pull up resistors trick the console into reading all 1's or all black for graphics. This is merely speculation, But an interesting find none the less. Actually...now that I think about it, the SNES version of Phantasy Star uses two 16-bit roms on the original japanese game. Surprisingly the translators found that the english text was stored only one ONE of the ROMs, which meant making a repro of that only needed one ROM switched. Sorry for that aside.

    In any case, I changed the region for my ps4 ROM around a couple times and it seems that the header does not effect the checksum. Oddly, the game has Brazil as the only region but I ran it on my USA-only BIOS and it runs perfectly. I even went as far as to change it to Europe and it still ran on a USA BIOS. The fact that you got sound and did not change the region says something about the game: Apparently it doesn't care what the region is. I have never come across a game like that.

    Where did you edit checksum? It should be at the check-mark and not the X:
    Spoiler warning:

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    Instead of J or U or E all the version I looked at had 4. They wouldn't run with a European Bios. Only USA. I was in a hurry so I just split and burned it anyway. YES 100% working on a genesis but not Megadrive. Savegame works and everything. I will try to region free the ROM and get it working with a European bios.

    I just replaced the 4 with J and followed by UE

    I edited where you showed me, checksum was OK. Still won't boot in Euro
    Last edited by wal666; 17th-January-2016 at 10:28. Reason: merged posts

  3. #153
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    Quote Originally Posted by wal666 View Post
    Instead of J or U or E all the version I looked at had 4. They wouldn't run with a European Bios. Only USA. I was in a hurry so I just split and burned it anyway. YES 100% working on a genesis but not Megadrive. Savegame works and everything. I will try to region free the ROM and get it working with a European bios.

    I just replaced the 4 with J and followed by UE

    I edited where you showed me, checksum was OK. Still won't boot in Euro
    It must one of those few games that determines Region from another location. I just tested the JAP ROM of the game on a Euro BIOS and it runs, so I am currently looking th the hex differences between the two ROMs.

    EDIT: So I started analyzing the hex of each ROM; J and U. I started looking at the code after the header where it starts to change. I believe that code starts running at 0x200, so the first difference from that point is at 0x358, wherein the U version performs several register compares, branch-if's and even some jump to subroutines before the code matches the J version. At 0x3F8 in Uv, the code matches the Jv at 0x359, but soon becomes different once again, but only slightly. I believe that it is around this area that the ROM is performing a region check but I am not familiar enough with 680000 op codes to hazard a guess.
    Here is the extra code found in the Uv:

    Download Links:
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    Another thing worth mentioning of the Uv, is that when the emulator displays the "NTSC only" message, the Pointer Counter remains in a very small loop forever. This program is located at 0x42076 - 0x4207A. Here is that code:

    Download Links:
    Links are hidden from guests. Please register to be able to view these links. which translates to:
    Download Links:
    Links are hidden from guests. Please register to be able to view these links. So it looks like it is testing Register B with the data $EF12 and if it not equal, it will branch back to 0x42076 forever.

    I speculate that if we could locate the main loop we could branch into that, but this is a lot of hex editing and I am not really prepared for that.

    I was using Regen emulator and viewing the 680000 dump while I also had both ROMs open in H x D to view.


    EDIT2:
    The infinite loop taht we get stuck in is a dead end. I edited it to break the loop and the console hangs. We need to hack the hex so that we never get in this loop in the first place.
    Download Links:
    Links are hidden from guests. Please register to be able to view these links. which translates to:
    Download Links:
    Links are hidden from guests. Please register to be able to view these links. I first altered the data at $EF12 to 00, so it would not be not-equal. - then it broke
    Then I tried to change the hex from 66FA to 67FA, which is BEQ instead of BNE. It again, broke.

    Im gonna see if I can change 66FA to Jump to subroutine or Jump address and see if we can get out of the loop and continue code at 0x3
    Last edited by Jazzmarazz; 19th-January-2016 at 04:44.

  4. #154
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    I just settler with the European ROM. Chips are soldered in now so that's how its gonna be.
    One thing I noticed is that both the PAL and NTSC ROM used the numbers instead of J,U OR E.

    On another note I have a database of all Genesis/Megadrive games that have saving capability as well as ROM size. I haven't sorted into different types of saving yet as I'm not 100% sure on some. It would be very helpful to the cart mod/repro community if this was made available somewhere.

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    Quote Originally Posted by wal666 View Post
    I just settler with the European ROM. Chips are soldered in now so that's how its gonna be.
    One thing I noticed is that both the PAL and NTSC ROM used the numbers instead of J,U OR E.

    On another note I have a database of all Genesis/Megadrive games that have saving capability as well as ROM size. I haven't sorted into different types of saving yet as I'm not 100% sure on some. It would be very helpful to the cart mod/repro community if this was made available somewhere.
    Wait, there is a PAL/European ROM? All I have in my collection is a U and J version so I assumed there wasn't one. Why am I missing it? ??
    Could you add your PAL ROM as an attachment for me? If you click go advance, there is a little paperclip button.

    That saving info would be helpful to share. From what I understand, those carts that "Hide" the RAM location are actually compatible with most any ROM that requires saving. Location of RAM is dependant on the end address of ROM, but a rewire of the highest address pins makes them all compatible. This of course excludes SSF2 and Serial eeprom-ram, but these only take up about 1% of all games and even then some of those serial eeprom games have mods to make them SRAM compatible.
    Last edited by Jazzmarazz; 19th-January-2016 at 13:42.

  6. #156
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    Sure thing, I will upload PAL ROM when I get home. For my next endeavour I would like to try and put an English SMS Phantasy Star ROM on a genesis cartridge, I can't figure out how to enable master system mode on the Megadrive.

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    Quote Originally Posted by wal666 View Post
    Sure thing, I will upload PAL ROM when I get home. For my next endeavour I would like to try and put an English SMS Phantasy Star ROM on a genesis cartridge, I can't figure out how to enable master system mode on the Megadrive.
    Haha, now thats gonna be a tough one. If you want that, you'll have to hand wire EVERY pin but I can try to help you. Not only that, but you will need one of the official mapper chips from an SMS or GG game and SRAM. If you don't have the mapper, you can only address 32KBytes of ROM and no RAM.

    I have only recently started exploring this kind of mod. What you want is the schematic of one of the official converters:

    http://www.raphnet.net/electronique/...d/index_en.php

    Raph here designed a simple passthrough based on one of the official passthrough carts. He open sourced the schematic too. Refer to the Schem: You'll notice that on the genesis side, /CART-IN and /S_RESET are both grounded. Normally only /CART-IN would be grounded. This is what I believe enables SMS mode, or z80 mode. Also A21 is pulled high and A22 is grounded. A23 is also pulled high and connected to an open button. Some of these address pins being pulled one way or the other may be associated with the pause button and not enabling SMS mode, however I cannot say which ones are which. It might just be best to follow them all.

    Here is what work I have done on this project:
    smstosmd.jpg

    I haven't tested it yet, but this is my design of a Mega Drive game with the ROm of an SMS game. Currently it only supports 32KBytes ROM until I can find donors for the mapper chip. I also don't know if it works as it is untested.

    EDIT: Sorry if the ROm area looks messy. I designed the cart to support a wide variety of EPROMs.
    Last edited by Jazzmarazz; 20th-January-2016 at 16:53.

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  9. #158
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    Phantasy Star IV (Europe.zip

    I have a few spare Master system carts with mappers.

    MAPPERS I HAVE ARE
    315-5235
    315-5208
    315-5365

    Could I use SRAM from a Genesis cartridge because I have HEAPS spare

    Im not scared to put the hours in to this!

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    Quote Originally Posted by wal666 View Post
    Phantasy Star IV (Europe.zip

    I have a few spare Master system carts with mappers.

    MAPPERS I HAVE ARE
    315-5235
    315-5208
    315-5365

    Could I use SRAM from a Genesis cartridge because I have HEAPS spare

    Im not scared to put the hours in to this!
    I found a photo here, you'll need to use the 315-5235 mapper.
    http://www.smspower.org/forums/15351...USBEPROMWriter
    http://www.smspower.org/forums/files...pcb_01_487.jpg

    Did the SMS version of phantasy Star come out for MegaDrive too?

    Yeah, any 6264 SRAM should work. Larger would work too, but you'll have to tie the higher address pins to either gnd or vcc. You can also see some extra resistors, diodes, capacitors and a transistor. I think this is for enabling/disabling the SRAM in low power mode. Do you have an extra BA6162? You can see that chip in one of those photos. It is a reset IC found on most saving-type SMD carts. That should be able to replace the extra components.

    Heres the pinout of the mapper:
    http://www.smspower.org/Development/MapperPinouts

    Also, take a good close look at the PS for SMD in those photos. You can see which pins are connected to VCC and which are connected to GND on the cart edge.
    Do you see that PLS153N, labelled "315-5342"?
    That is a commercially available PLA. It looks like they mention it in taht thread too. I have to sleep now but see if you can find more info on that chip. Has the hex been dumped? They could easily be reproduced for development or flash carts so we could make ANY SMS game on SMD.

    I'll have to buy myself a PS for SMD now.

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    Quote Originally Posted by wal666 View Post
    You know what, It's not used as a mapper at all. The chip sets up the stack pointer which you probably have to do for Phantasy star. I don't think you need a mapper at all because of the enormous amount of memory the Mega Drive is already able to map. However Rap tested PS and listed it as compat with the MD controller and Stack pointer "OK".

    I have to do more research on this. I really need a copy of a game with that PLS153 chip.

    EDIT:
    UGH
    Sorry to be the bearer of bad news but the 315-5342 (on the Mega Drive PS1 cartridge) is not a mapper chip. The mapper is internal to the MPR-16266-F (it's an MB834011, an custom chip which has MASK ROM + SEGA mapper built in a single die).

    315-5342 is the PLD chip used on the Power base converter to set up the CPU stack before executing the game.

    So basically, the MD one won't work for you.
    SEGA did the same darn thing with GG. Bugs the hell outta me.
    Last edited by Jazzmarazz; 21st-January-2016 at 17:07.

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    Well I am only updating not because anybody assisted in my problem but for the people who may have the same problem as I did and are struggling. The problem appears to have been not using an external power supply. Even though the manufacturer swears up and down left and right one is not needed, it is. I programmed with an external power supply and it worked.

    Good info here, I just wish someone would have at least acknowledged I asked a question. It is what it is.

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    OK so here is the progress I have made with getting phantasy star on to a megadrive/genesis cartridge.
    First I build a pin converter from master system 50pin to Megadrive 64pin. This works very well with most master system games.
    Then I put phantasy star on a 32pin 27c040 EPROM and got it working on a monopoly PCB with some extra wiring.
    This monopoly phantasy star works on master system, game gear with converter and Megadrive with my homemade pin converter.
    All I have to do is put this mess on a pcb.
    As far as setting up stack pointer phantasy star doesn't need it but I bought an official power base converter anyway so I can dump the 315-5342 for use later on.

  15. #164
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    Quote Originally Posted by icemanxp300 View Post
    Well I am only updating not because anybody assisted in my problem but for the people who may have the same problem as I did and are struggling. The problem appears to have been not using an external power supply. Even though the manufacturer swears up and down left and right one is not needed, it is. I programmed with an external power supply and it worked.

    Good info here, I just wish someone would have at least acknowledged I asked a question. It is what it is.
    Sorry I missed your question. it seems that it was a while ago.
    There is only me for answering questions.

    Quote Originally Posted by wal666 View Post
    OK so here is the progress I have made with getting phantasy star on to a megadrive/genesis cartridge.
    First I build a pin converter from master system 50pin to Megadrive 64pin. This works very well with most master system games.
    Then I put phantasy star on a 32pin 27c040 EPROM and got it working on a monopoly PCB with some extra wiring.
    This monopoly phantasy star works on master system, game gear with converter and Megadrive with my homemade pin converter.
    All I have to do is put this mess on a pcb.
    As far as setting up stack pointer phantasy star doesn't need it but I bought an official power base converter anyway so I can dump the 315-5342 for use later on.
    Thats awesome. Can we get some photos? Im interested.

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