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Hey im going to program my first chip soon, I Opnede one of my sms games and there is space for one 28 pin chip, and here is my question what RAM chip should I choose for my homebrew's? It could be nice with the largest one which fits in it.

If it exceed the 32kb im aware of that I need to set up banking. I use WLA DX and I just want an exampel of how to set up banking for the choosen chip and pretty much how to put code in the different banks and how to access it so it goes into page2/frame2/slot2 or whatever you call it. (I am really lost on this banking thingy btw.) If just someone could give me an exampel of their banking with your farvorite chip which fit in my print with 28 pin holes.

The banking is made of external hardware, which is usually embedded into typical Sega ROM chips, but its not present in typical memory chips you would use in the SMS cart. I have worked out a mapper, but I've yet to test it out. Its made of 6 logic chips and load of wires......

If the memory chips all have CS pins, you could always use a PIC to generate a chip code, and ideally use upwards of 65,536 chips. Tell me what memory chip you intend on using. I'm not familiar with SEGA code, but I can certainly do the electronics side if someone wants to write the identi code.

So with my print board which only got one socket for a 28 pin chip the maximum RAM capacity is 32kb because banking not is an option on it or what?

XBrav I have not intentions of making a new catridge I just what to know which chip the sms programmers would use on the printbroard with one socket of 28 pins which I found in one of my catridges.

jensjoachim wrote

So with my print board which only got one socket for a 28 pin chip the maximum RAM capacity is 32kb because banking not is an option on it or what?

XBrav I have not intentions of making a new catridge I just what to know which chip the sms programmers would use on the printbroard with one socket of 28 pins which I found in one of my catridges.

Sorry for the misunderstanding. I'd assume you're limited to 32kb unless you can build an addressing system on top of it... Seems unusual given that 32kb is a 15 bit addressing system, not common at all.

Sorry, mindless babble.

jensjoachim wrote

So with my print board which only got one socket for a 28 pin chip the maximum RAM capacity is 32kb because banking not is an option on it or what?

XBrav I have not intentions of making a new catridge I just what to know which chip the sms programmers would use on the printbroard with one socket of 28 pins which I found in one of my catridges.

Do you want to replace the 28-pin chip with an EPROM? If so, what kind of EPROM are you using - perhaps a 27C256 (32K) or 27C512 (64K?) Both are 28 pins and would fit.

Due to the way the cartridge is wired, regardless of the EPROM you use only 32K is available. It will be mapped to the first 32K of the SMS address space (0000-7FFF).

If you use a 27C512, you will need to make sure your program fits within the first 32K, and then duplicate that into the latter 32K. This is because the 27C512 has a slight conflict with the pin assignments of the 28-pin chip you are removing from the cartridge.

Yes I want to replace the chip with EPROM I dont want it to get to advanced.

Quote

If you use a 27C512, you will need to make sure your program fits within the first 32K, and then duplicate that into the latter 32K. This is because the 27C512 has a slight conflict with the pin assignments of the 28-pin chip you are removing from the cartridge

Is the because we cant rely on the last adress pin?

But anyways I can't count because when I looked further on my print I noticed it was 32 pin socket on the print instead og 28 pin. Then I did some research and I just want to know if EPROM 27C010 fits into that? And if it does I gues I have to dublicate it 4 times because its 128kb.

If this above isnt possible i want to ask if there is a list of all sega games which tells what chips is inside so I wont have to open all my catridges to find a catridge print with a single 28 socket spot on it.

Quote

Is the because we cant rely on the last adress pin?

Not quite, the 28-pin socket has Z80 /WR assigned to pin 1. On a 27C512 EPROM, pin 1 is A15. Now during a read /WR should always be 1, but to be on the safe side it can't hurt to fill both the lower and upper halves of the EPROM with the same data.

Quote

it was 32 pin socket on the print instead og 28 pin. Then I did some research and I just want to know if EPROM 27C010 fits into that? And if it does I gues I have to dublicate it 4 times because its 128kb.

In theory it should work, and you would duplicate it. But to be safe I would make the following modifications:

Pin 1 is connected to ground. It should be connected to +5V instead.
Pins 2,31 are no-connects (assuming your board does not have battery backed RAM). You should tie pin 2 to ground and pin 31 to +5V.

This sets VPP=+5V, A16=GND, PGM#=+5V.

Quote

If this above isnt possible i want to ask if there is a list of all sega games which tells what chips is inside so I wont have to open all my catridges to find a catridge print with a single 28 socket spot on it.

As a general rule:

- All games that are 1 Megabit or smaller will have a 28-pin chip.
- All games that are bigger will have a 32-pin chip.

But some could have a mapper chip included instead of a single ROM.

Quote

Not quite, the 28-pin socket has Z80 /WR assigned to pin 1. On a 27C512 EPROM, pin 1 is A15. Now during a read /WR should always be 1, but to be on the safe side it can't hurt to fill both the lower and upper halves of the EPROM with the same data.

So I gues with a little simple modification such as a button to switch between ground and vcc I could actually burn 2 projects at the time.

Quote

As a general rule:

- All games that are 1 Megabit or smaller will have a 28-pin chip.
- All games that are bigger will have a 32-pin chip.

But some could have a mapper chip included instead of a single ROM.

Did someone post a list for that or should I be able to tjek the size in an emulator if I get the ROM. In this case what emulator then?

I also got surprised when I opened Action Fighter when I only found one chip because I was about to se if it was possible for me to make a 1M catridge with the paging chip 315-5208. Makes me a little mude since I kinda forced it up :/

2 pics of my mapper. I would be using my 4Mbyte MD flashcart with it, hence it having MD compatible pinout on the cartslot on top.... I have to add SMS connector on bottom and try it out... its been like so for over a year now D:
http://www.fileden.com/files/2008/4/21/1876835/SMSmapperFront.jpg
http://www.fileden.com/files/2008/4/21/1876835/SMSmapperBack.jpg

jensjoachim wrote

Quote

Not quite, the 28-pin socket has Z80 /WR assigned to pin 1. On a 27C512 EPROM, pin 1 is A15. Now during a read /WR should always be 1, but to be on the safe side it can't hurt to fill both the lower and upper halves of the EPROM with the same data.

So I gues with a little simple modification such as a button to switch between ground and vcc I could actually burn 2 projects at the time.

Sure, if you disconnected pin 1 of the 28-pin socket from /WR and connected it to a SPDT switch.

Quote

Did someone post a list for that or should I be able to tjek the size in an emulator if I get the ROM. In this case what emulator then?

I don't think there is a list.

In my experience the 28-pin chips are 128K max (1 megabit), and anything bigger uses a 32-pin chip (128K to 512K max, 1/2/4 megabit).

So while it isn't guaranteed, it is likely a 1-megabit game uses a 28-pin chip. But not always the case.

Quote

I also got surprised when I opened Action Fighter when I only found one chip because I was about to se if it was possible for me to make a 1M catridge with the paging chip 315-5208. Makes me a little mude since I kinda forced it up :/

Darn, that's too bad. I wish there was an easy way to tell what was on the inside. All you can do is buy the game and open it up to see.

Thx for the information TmEE but its a little to advanced for me but it might comes sooner or later when 32kb isnt enough.

And thanks for the help Charles now everything should be set for my first homebrew to catridge. Actually I just brought a programmer and some chips so I should be all ready when my stuff arives.

Author	Message
jensjoachim Joined: 16 Jul 2009 Posts: 30 Location: Denmark	Chip select and banking setup Posted: Thu Aug 20, 2009 6:55 pm
	Hey im going to program my first chip soon, I Opnede one of my sms games and there is space for one 28 pin chip, and here is my question what RAM chip should I choose for my homebrew's? It could be nice with the largest one which fits in it. If it exceed the 32kb im aware of that I need to set up banking. I use WLA DX and I just want an exampel of how to set up banking for the choosen chip and pretty much how to put code in the different banks and how to access it so it goes into page2/frame2/slot2 or whatever you call it. (I am really lost on this banking thingy btw.) If just someone could give me an exampel of their banking with your farvorite chip which fit in my print with 28 pin holes.

TmEE Joined: 31 Oct 2007 Posts: 853 Location: Estonia, Rapla city	Posted: Thu Aug 20, 2009 7:22 pm
	The banking is made of external hardware, which is usually embedded into typical Sega ROM chips, but its not present in typical memory chips you would use in the SMS cart. I have worked out a mapper, but I've yet to test it out. Its made of 6 logic chips and load of wires......

XBrav Joined: 20 Aug 2009 Posts: 2 Location: Calgary	Posted: Thu Aug 20, 2009 7:43 pm
XBrav Joined: 20 Aug 2009 Posts: 2 Location: Calgary	If the memory chips all have CS pins, you could always use a PIC to generate a chip code, and ideally use upwards of 65,536 chips. Tell me what memory chip you intend on using. I'm not familiar with SEGA code, but I can certainly do the electronics side if someone wants to write the identi code.

jensjoachim Joined: 16 Jul 2009 Posts: 30 Location: Denmark	Posted: Thu Aug 20, 2009 7:49 pm
	So with my print board which only got one socket for a 28 pin chip the maximum RAM capacity is 32kb because banking not is an option on it or what? XBrav I have not intentions of making a new catridge I just what to know which chip the sms programmers would use on the printbroard with one socket of 28 pins which I found in one of my catridges.

XBrav Joined: 20 Aug 2009 Posts: 2 Location: Calgary	Posted: Thu Aug 20, 2009 7:56 pm
XBrav Joined: 20 Aug 2009 Posts: 2 Location: Calgary	jensjoachim wrote So with my print board which only got one socket for a 28 pin chip the maximum RAM capacity is 32kb because banking not is an option on it or what? XBrav I have not intentions of making a new catridge I just what to know which chip the sms programmers would use on the printbroard with one socket of 28 pins which I found in one of my catridges. Sorry for the misunderstanding. I'd assume you're limited to 32kb unless you can build an addressing system on top of it... Seems unusual given that 32kb is a 15 bit addressing system, not common at all. Sorry, mindless babble.

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Fri Aug 21, 2009 4:49 am
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	jensjoachim wrote So with my print board which only got one socket for a 28 pin chip the maximum RAM capacity is 32kb because banking not is an option on it or what? XBrav I have not intentions of making a new catridge I just what to know which chip the sms programmers would use on the printbroard with one socket of 28 pins which I found in one of my catridges. Do you want to replace the 28-pin chip with an EPROM? If so, what kind of EPROM are you using - perhaps a 27C256 (32K) or 27C512 (64K?) Both are 28 pins and would fit. Due to the way the cartridge is wired, regardless of the EPROM you use only 32K is available. It will be mapped to the first 32K of the SMS address space (0000-7FFF). If you use a 27C512, you will need to make sure your program fits within the first 32K, and then duplicate that into the latter 32K. This is because the 27C512 has a slight conflict with the pin assignments of the 28-pin chip you are removing from the cartridge.

jensjoachim Joined: 16 Jul 2009 Posts: 30 Location: Denmark	Posted: Fri Aug 21, 2009 4:01 pm
	Yes I want to replace the chip with EPROM I dont want it to get to advanced. Quote If you use a 27C512, you will need to make sure your program fits within the first 32K, and then duplicate that into the latter 32K. This is because the 27C512 has a slight conflict with the pin assignments of the 28-pin chip you are removing from the cartridge Is the because we cant rely on the last adress pin? But anyways I can't count because when I looked further on my print I noticed it was 32 pin socket on the print instead og 28 pin. Then I did some research and I just want to know if EPROM 27C010 fits into that? And if it does I gues I have to dublicate it 4 times because its 128kb. If this above isnt possible i want to ask if there is a list of all sega games which tells what chips is inside so I wont have to open all my catridges to find a catridge print with a single 28 socket spot on it.

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Sat Aug 22, 2009 5:00 am
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Quote Is the because we cant rely on the last adress pin? Not quite, the 28-pin socket has Z80 /WR assigned to pin 1. On a 27C512 EPROM, pin 1 is A15. Now during a read /WR should always be 1, but to be on the safe side it can't hurt to fill both the lower and upper halves of the EPROM with the same data. Quote it was 32 pin socket on the print instead og 28 pin. Then I did some research and I just want to know if EPROM 27C010 fits into that? And if it does I gues I have to dublicate it 4 times because its 128kb. In theory it should work, and you would duplicate it. But to be safe I would make the following modifications: Pin 1 is connected to ground. It should be connected to +5V instead. Pins 2,31 are no-connects (assuming your board does not have battery backed RAM). You should tie pin 2 to ground and pin 31 to +5V. This sets VPP=+5V, A16=GND, PGM#=+5V. Quote If this above isnt possible i want to ask if there is a list of all sega games which tells what chips is inside so I wont have to open all my catridges to find a catridge print with a single 28 socket spot on it. As a general rule: - All games that are 1 Megabit or smaller will have a 28-pin chip. - All games that are bigger will have a 32-pin chip. But some could have a mapper chip included instead of a single ROM.

jensjoachim Joined: 16 Jul 2009 Posts: 30 Location: Denmark	Posted: Sat Aug 22, 2009 7:18 am
	Quote Not quite, the 28-pin socket has Z80 /WR assigned to pin 1. On a 27C512 EPROM, pin 1 is A15. Now during a read /WR should always be 1, but to be on the safe side it can't hurt to fill both the lower and upper halves of the EPROM with the same data. So I gues with a little simple modification such as a button to switch between ground and vcc I could actually burn 2 projects at the time. Quote As a general rule: - All games that are 1 Megabit or smaller will have a 28-pin chip. - All games that are bigger will have a 32-pin chip. But some could have a mapper chip included instead of a single ROM. Did someone post a list for that or should I be able to tjek the size in an emulator if I get the ROM. In this case what emulator then? I also got surprised when I opened Action Fighter when I only found one chip because I was about to se if it was possible for me to make a 1M catridge with the paging chip 315-5208. Makes me a little mude since I kinda forced it up :/

TmEE Joined: 31 Oct 2007 Posts: 853 Location: Estonia, Rapla city	Posted: Sat Aug 22, 2009 1:20 pm
	2 pics of my mapper. I would be using my 4Mbyte MD flashcart with it, hence it having MD compatible pinout on the cartslot on top.... I have to add SMS connector on bottom and try it out... its been like so for over a year now D: http://www.fileden.com/files/2008/4/21/1876835/SMSmapperFront.jpg http://www.fileden.com/files/2008/4/21/1876835/SMSmapperBack.jpg

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Sun Aug 23, 2009 3:31 am
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	jensjoachim wrote Quote Not quite, the 28-pin socket has Z80 /WR assigned to pin 1. On a 27C512 EPROM, pin 1 is A15. Now during a read /WR should always be 1, but to be on the safe side it can't hurt to fill both the lower and upper halves of the EPROM with the same data. So I gues with a little simple modification such as a button to switch between ground and vcc I could actually burn 2 projects at the time. Sure, if you disconnected pin 1 of the 28-pin socket from /WR and connected it to a SPDT switch. Quote Did someone post a list for that or should I be able to tjek the size in an emulator if I get the ROM. In this case what emulator then? I don't think there is a list. In my experience the 28-pin chips are 128K max (1 megabit), and anything bigger uses a 32-pin chip (128K to 512K max, 1/2/4 megabit). So while it isn't guaranteed, it is likely a 1-megabit game uses a 28-pin chip. But not always the case. Quote I also got surprised when I opened Action Fighter when I only found one chip because I was about to se if it was possible for me to make a 1M catridge with the paging chip 315-5208. Makes me a little mude since I kinda forced it up :/ Darn, that's too bad. I wish there was an easy way to tell what was on the inside. All you can do is buy the game and open it up to see.

jensjoachim Joined: 16 Jul 2009 Posts: 30 Location: Denmark	Posted: Sun Aug 23, 2009 9:37 pm
	Thx for the information TmEE but its a little to advanced for me but it might comes sooner or later when 32kb isnt enough. And thanks for the help Charles now everything should be set for my first homebrew to catridge. Actually I just brought a programmer and some chips so I should be all ready when my stuff arives.

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