[GUIDE] Make a Reprogrammable Genesis Cart

[Lotaphi]

1. That is not a resistor, it is a jumper. You can tell becusse of the single black stripe. You're probably thinking "that's odd" but it was quite common to use since pick-and-place machines could grab them and place them.

2. Did you "byte-swap" the rom image before programming it?

Nope. This is the first I have heard of doing this. I do this with my SNES repros but I don't know how to do it with genesis. can you help me please?

Never mind. I went back and reread your stop about the software and read about how to byte-swap there! works perfectly now!. I skipped that step beffore because we have different programmers so I thought it was going to be specific to your programmer. dumb me. thanks for the great guide!

[Jazzmarazz]

Nope. This is the first I have heard of doing this. I do this with my SNES repros but I don't know how to do it with genesis. can you help me please?

Never mind. I went back and reread your stop about the software and read about how to byte-swap there! works perfectly now!. I skipped that step beffore because we have different programmers so I thought it was going to be specific to your programmer. dumb me. thanks for the great guide!

Great work! What programmer do you have? I just got a new gq-4x for all of my repro needs. My tutorials may be based on that from now on.

[Lotaphi]

Great work! What programmer do you have? I just got a new gq-4x for all of my repro needs. My tutorials may be based on that from now on.

That's what I have and it worked great. one of the burns I did though didn't burn the chip correctly for some reason. it was my 2nd eprom I tried where I padded the rom thinking that was the problem. it had a bunch of FF randomly in the wrong places when I hex compared it. other then that one time they have worked well.

[XC-3730C]

Is there some sort of newbie's guide to what is needed to start doing your own repo's and DIY flash carts)? I am slowly getting out of console modding (TSOP Xbox's, GameCube XenoGC's, Dreamcast HDD mods, etc), and want to get into doing my own repo's and DIY flash carts.

[Lotaphi]

Seriously? Just USB power for a 27c322? That is great. The uv-eproms need high voltage for their vpp pin. That's great that usb power can handle these chips.

yep, so far the only ones that it said it needs power for are actually the older smaller chips for atari 2600 sized games. Though I haven't researched wether or not using power for things that don't need it adds any benefits such as faster burning or more stability.



Jazzmarazz, I have a question. I have a bunch of genesis boards with batteries on them and a lot of 27c322 eproms. how do I get this to work right? it didn't seem to work as easily as getting a non sram game working. most of the boards with batteries are all different too. Is there some universal way to get 27c322 to work on any of them to make games that need save functions?

Edit: So this was once again an issue with my not remembering/fully reading things again and it was because I didn't wire A20 (pin 32) of the 27C322 to pin 5 of the 74H00 IC. Now I need to see if I can get it to save (which I haven't tested yet, but it works now)

Edit 2: After testing it a few times it doesn't seem like it's saving correctly. I think the battery is working as it reads 3v using my multimeter so I'm not sure at this point what to do as I can't find any info on save issues using 27c322

[Jazzmarazz]

yep, so far the only ones that it said it needs power for are actually the older smaller chips for atari 2600 sized games. Though I haven't researched wether or not using power for things that don't need it adds any benefits such as faster burning or more stability.



Jazzmarazz, I have a question. I have a bunch of genesis boards with batteries on them and a lot of 27c322 eproms. how do I get this to work right? it didn't seem to work as easily as getting a non sram game working. most of the boards with batteries are all different too. Is there some universal way to get 27c322 to work on any of them to make games that need save functions?

Edit: So this was once again an issue with my not remembering/fully reading things again and it was because I didn't wire A20 (pin 32) of the 27C322 to pin 5 of the 74H00 IC. Now I need to see if I can get it to save (which I haven't tested yet, but it works now)

Edit 2: After testing it a few times it doesn't seem like it's saving correctly. I think the battery is working as it reads 3v using my multimeter so I'm not sure at this point what to do as I can't find any info on save issues using 27c322

Looking back on my tutorial, that may be the problem. My statement is ambiguous as to whether the eeprom connects to pin 5 of the logic or if the cart edge connects to the logic.
Pin 5 of the 74xx00 is an input, not an output. So what we are doing here is connecting two inputs together - nothing happens.



The 74xx00 is being used as a simple logic-based memory mapper comprised of only NAND gates (not and). The locations within the memory map for each IC can be determined with some logic equations. For example (not literally, but probably close):

IC_ROM = ~(CE*A20)
IC_RAM = ~CE*A20

So (still not being literal) when CE is low and A20 is low, ROM is enabled. When CE is low and A20 is high, RAM is enabled (ROM is disabled). That being said, we should be using A21 and not A20 if you want 2MBytes of ROM. A20 on the cart edge is actually A21 and 2^21 equals 2Mbytes which is split in half for each IC. The first 1Mbyte is allocated to ROM and the second 1MByte is allocated to RAM. I realize this is a bit much and difficult to explain.

What I mean to say is that I should edit my tutorial and be more clear. no one has questioned it before, so I guess it stayed incorrect for a long time. hehe

So.....

To clear everything up, first, what game are you trying to burn? How big is it? Does it only fill half of the 27c322? If the game is only 1Mbyte, we can connect pin A20 of your eeprom to ground and solve the issue. I think.

If your game is actually 2Mbytes, we will have to work a little harder.

[Lotaphi]

Thanks for the info. So it seems like every game so far that I want to make is 2Mbytes unfortunately.

[rodragonbr]

Looking back on my tutorial, that may be the problem. My statement is ambiguous as to whether the eeprom connects to pin 5 of the logic or if the cart edge connects to the logic.
Pin 5 of the 74xx00 is an input, not an output. So what we are doing here is connecting two inputs together - nothing happens.



The 74xx00 is being used as a simple logic-based memory mapper comprised of only NAND gates (not and). The locations within the memory map for each IC can be determined with some logic equations. For example (not literally, but probably close):

IC_ROM = ~(CE*A20)
IC_RAM = ~CE*A20

So (still not being literal) when CE is low and A20 is low, ROM is enabled. When CE is low and A20 is high, RAM is enabled (ROM is disabled). That being said, we should be using A21 and not A20 if you want 2MBytes of ROM. A20 on the cart edge is actually A21 and 2^21 equals 2Mbytes which is split in half for each IC. The first 1Mbyte is allocated to ROM and the second 1MByte is allocated to RAM. I realize this is a bit much and difficult to explain.

What I mean to say is that I should edit my tutorial and be more clear. no one has questioned it before, so I guess it stayed incorrect for a long time. hehe

So.....

To clear everything up, first, what game are you trying to burn? How big is it? Does it only fill half of the 27c322? If the game is only 1Mbyte, we can connect pin A20 of your eeprom to ground and solve the issue. I think.

If your game is actually 2Mbytes, we will have to work a little harder.

Hi,

First thanks for the awesome tutorial.

Do you have any news on this problem? I tryed to make an Shining Force 2 with this board, wired the A20 of the 27c322 to the pin 5 of the 74HC but it not worked.
I lifted the pin, and solded directly to the pin 5 with a wire.

Another question, im trying to translate an Shining force 1 from japanese to portuguese, with the original PCB, it have 2 ROMS, I desolded both and solded an 27c160 with the full game (1.5mb) on the botton slot, and it not works.

I made various no save games with success, but the saving ones are giving me headaches.

Best Regards,

Rodrigo
P.S.: Sorry for my bad english

[Jazzmarazz]

Ok, that's fine. What we should do is figure out how they are being mapped.
Lets start by choosing one board, looking at the 74hc00 IC and trace back all of the inputs and outputs. Please look at that diagram I posted above and write down where each pin goes:

1 - GND
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
10 -
11 -
12 -
13 -
14 - VCC

Then we can determine which ones to lift and rewire. It should be pretty simple if you have a multimeter with continuity checker. Some of the inputs may be bridge together and connected to address pins on the cart edge. Some may simply be connected to either vcc or gnd with the outputs floating, but we won't know until you check.

Do you know what a truth table is? It looks like so:
http://sub.allaboutcircuits.com/imag...z/02772x02.png

we will make one of our own that pertains to our project once you trace those pins for us.

[Lotaphi]

So what two points am I checking for continuity for? between the 74HC00 and the sram, board connections or eprom?

[Jazzmarazz]

So what two points am I checking for continuity for? between the 74HC00 and the sram, board connections or eprom?

I would like to know where all of the pin on the 74hc00 go:

1 - GND
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
10 -
11 -
12 -
13 -
14 - VCC

This will tell us how the board is mapping the locations of ROM and RAM, then we can modify the map for 2MBytes of ROM and keep the RAM after it.

I assume you will find cart edge pins like A21 and ~CE connecting to some of the inputs of the 7400. Some of the outputs from the 7400 will connect to ~CE of ROM and ~CE of RAM.

[Jazzmarazz]

updated photos in original post.

[wal666]

Hello there.. Thanks for all the info, it has been very useful. Can I buy a Japanese phantasy star IV cartridge and put the English version on it ? Are the PCB the same? I understand there is 2 mask ROMs so how do I go about splitting the ROM to put it on 2 EPROMS? Any help would be much appreciated

[Jazzmarazz]

Hello there.. Thanks for all the info, it has been very useful. Can I buy a Japanese phantasy star IV cartridge and put the English version on it ? Are the PCB the same? I understand there is 2 mask ROMs so how do I go about splitting the ROM to put it on 2 EPROMS? Any help would be much appreciated

You could do that if you wanted to. It is likely that you could use most any cartridge that you could find for much cheaper. Lets have a look at the game in question. According to uCON64:

uCON64 2.0.0 Win32 (MinGW) 1999-2005
Uses code from various people. See 'developers.html' for more!
This may be freely redistributed under the terms of the GNU Public License

C:\Users\Jordan\Desktop\Phantasy Star IV (USA).md

Magicom/BIN/RAW

00000100 53 45 47 41 20 47 45 4e 45 53 49 53 20 20 20 20 SEGA GENESIS
00000110 28 43 29 53 45 47 41 20 31 39 39 34 2e 4e 4f 56 (C)SEGA 1994.NOV
00000120 50 48 41 4e 54 41 53 59 20 53 54 41 52 20 54 68 PHANTASY STAR Th
00000130 65 20 65 6e 64 20 6f 66 20 74 68 65 20 6d 69 6c e end of the mil
00000140 6c 65 6e 6e 69 75 6d 20 20 20 20 20 20 20 20 20 lennium
00000150 50 48 41 4e 54 41 53 59 20 53 54 41 52 20 54 68 PHANTASY STAR Th
00000160 65 20 65 6e 64 20 6f 66 20 74 68 65 20 6d 69 6c e end of the mil
00000170 6c 65 6e 6e 69 75 6d 20 20 20 20 20 20 20 20 20 lennium
00000180 47 4d 20 4d 4b 2d 31 33 30 37 20 2d 30 30 05 cb GM MK-1307 -00..
00000190 4a 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 J
000001a0 00 00 00 00 00 2f ff ff 00 ff 00 00 00 ff ff ff ...../..........
000001b0 52 41 f8 20 00 20 00 01 00 20 3f ff 20 20 20 20 RA. . ... ?.
000001c0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
000001d0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
000001e0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
000001f0 34 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 4

Genesis/Sega Mega Drive/Sega CD/32X/Nomad
PHANTASY STAR The end of the millennium
Sega
Brazil
3145728 Bytes (24.0000 Mb)

Padded: Maybe, 46572 Bytes (0.3553 Mb)
Interleaved/Swapped: No
Backup unit/emulator header: No
Japanese game name: PHANTASY STAR The end of the millennium
Date: 1994.NOV
Internal size: 24.0000 Mb
ROM start: 00000000
ROM end: 002fffff
Cartridge RAM: Yes, 15 kBytes (backup)
RAM start: 00200001
RAM end: 00203fff
Product type: Game
I/O device(s): 3 Button Pad
Modem data:
Memo:
Product code: MK-1307
Version: 1.00
Checksum: Ok, 0x05cb (calculated) == 0x05cb (internal)
Checksum (CRC32): 0xfe236442

The information above shows that the game seems pretty typical. 24MegaBits, or 3MBytes starting at address 0x00000000 to 0x002fffff and has SRAM. However, SRAM is located at 0x00200001 to 0x00203FFF. You'll notice that SRAM overlaps with the ROM, so you'll need a slightly different cart. One such cart is descirbed in detail here:
http://forums.nesdev.com/viewtopic.p...11615&start=15
So the Japanese copy would probably be easiest to mod. I don't see many carts like that one. In fact I don't have any as far as I know. if you come across another cartridge with two ROMs, one SRAM a 74ls74 and 74ls139, let me know. We can rewire it if need be.

[wal666]

Wow thanks for the reply. I'm not home at the moment but I'm pretty sure I have one similar (2 mask ROMs, SRAM and a couple of other chips). I will take pics when I can. Its a baseball game I think

The Story Of Thor and Phantasy Star 4 are the only 2 that have this board apparently

[ATTACH=CONFIG]48174[/ATTACH

Attachment 48175

That is world series baseball 95. According to my ROMs list this is 3mb, could this possibly be reworked?