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I find useful to have my own utility ROMs loaded before the cartridge but don't want to remove the original SMS BIOS ROM so I decided to make a SegaCard replacement.

So far I designed it to be the bare minimum ROM, using only a ROM chip and space for a logic gate/PLD chip. Board space is scarce but I could use suggestions or help with potential issues before sending it to production.

Is Working!
Current prototype has been able to play SLOT2 games and SLOT1/2 games on an unmodified european Master System from the card SLOT. Some games presume the ROM is loaded on the cartridge slot (Bubble Bobble) and require a minor patch. (Mapper design thread)

Relevant design decissions/known issues:
- ROM socket accepts SST39SF040 or pin compatible
- ROM !CE line is driven by (!CE || !M0-7)
- U2/U3 accepts a 74LS32 IC or a correctly programmed ATF16V8 PLD
- Card length is below 100mm to have cheaper production costs.

board.png (53.73 KB)

Board

SegaCard - CADCAM.ZIP (21.39 KB)

Gerber files

What will be the largest ROM it would support?

Without further hardware, 32/48K. Using a 74LS32 you are limited to 32K, using the 16V8 you could get an extra 16K however it should be enough for its intended purpose of loading tool ROMs before a cartridge.

I see. Well, I was wondering how hard would be to turn that (also) into a way to distribute new games. Would it be possible to have an (even minimal) mapper onboard?

A minimal (non SEGA mapper-like) mapper can be done adding just two discrete ICs. I am fairly sure a minimal 1MB SEGA mapper can be done as well with discrete ICs or a mixture of discretes and a fast MCU.

I am working on it for a custom cartridge. If I succeed I can port it to the card as well.

Boards arrived!

Made the "i am new at this" mistake of making the PCB too close to the card slot width so it does not enter quite as easy at it should (it scratches the slot sides) but a light sanding of the board edges solvers the problem. Mapper testing starts today :D

Design using two boards is intentional, the bottom board has the contacts the flash IC and space for a PLD connected to the Address bus and another PLD on the CPU signals, exposing address bus, data bus and many of the signals on the pins where the upper board where the mapper logic itself is implemented. Worst case scenario I'd need to make modifications to the upper board.

card.jpg (290.77 KB)

First test with 32K ROM is working. Card fits nicely on the SMS card slot (see attachment).

Will try getting SLOT2 mapping today.

IMG_20161111_204012.jpg (2.97 MB)

Cool. Not a fan of SMD? :)

IT WORKS! SEGA Card with SEGA mapper but using none of the original hardware (nor any fancy FPGA ;)

Marble Madness running off the card slot with SLOT2 mapping! There is still an unknown bug with SLOT1 mapping but is working! Will try fixing SLOT1 any time soon.

P.S. Is there any list of SLOT2-Only games? Is this list exhaustive?

Quote

Not a fan of SMD?

Prototyping is easier with DIP, and I _had_ to make some minor hardware fixes ;)

IMG_20161113_172757.jpg (2.34 MB)

NeonMan wrote

P.S. Is there any list of SLOT2-Only games?

devkitSMS supports only slot 2 thus any ROM bigger than 48KB in the linked list is surely using slot 2 mapper.

The slot 2 paging list is not exhaustive, lots of games have not been checked.

I'll probably have SLOT1 fixed in the next days anyway. Meanwhile I've been testing some games on the list. So far I tested "Marble Madness" and "Sonic the Hedgehog 2" with no issue.

I am not sure if the Card/Catridge difference would create any issue with certain games. So far these two had no issue.

My god man.
This stuff's amazing.

Now we wait and refine until it's as thin as we can get it :)

Is working!

Full SLOT1 / SLOT2 support, works on unmoddified european Master System.

Tested it with a known SLOT1 /2 game, ECCO the dolphin, and have had no issue so far.

Tested Bubble Bobble as well, which requires a minor patch to work from the Card slot.

Author	Message
NeonMan Joined: 24 Sep 2013 Posts: 141	SegaCard clone [Working SLOT1/2 prototype] Posted: Tue Oct 11, 2016 10:26 pm Last edited by NeonMan on Mon Jan 16, 2017 12:11 am; edited 7 times in total
NeonMan Joined: 24 Sep 2013 Posts: 141	I find useful to have my own utility ROMs loaded before the cartridge but don't want to remove the original SMS BIOS ROM so I decided to make a SegaCard replacement. So far I designed it to be the bare minimum ROM, using only a ROM chip and space for a logic gate/PLD chip. Board space is scarce but I could use suggestions or help with potential issues before sending it to production. Is Working! Current prototype has been able to play SLOT2 games and SLOT1/2 games on an unmodified european Master System from the card SLOT. Some games presume the ROM is loaded on the cartridge slot (Bubble Bobble) and require a minor patch. (Mapper design thread) Relevant design decissions/known issues: - ROM socket accepts SST39SF040 or pin compatible - ROM !CE line is driven by (!CE \|\| !M0-7) - U2/U3 accepts a 74LS32 IC or a correctly programmed ATF16V8 PLD - Card length is below 100mm to have cheaper production costs. board.png (53.73 KB) Board SegaCard - CADCAM.ZIP (21.39 KB) Gerber files

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	Posted: Wed Oct 12, 2016 7:28 am
	What will be the largest ROM it would support?

NeonMan Joined: 24 Sep 2013 Posts: 141	Posted: Wed Oct 12, 2016 10:32 am
NeonMan Joined: 24 Sep 2013 Posts: 141	Without further hardware, 32/48K. Using a 74LS32 you are limited to 32K, using the 16V8 you could get an extra 16K however it should be enough for its intended purpose of loading tool ROMs before a cartridge.

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	Posted: Wed Oct 12, 2016 11:15 am
	I see. Well, I was wondering how hard would be to turn that (also) into a way to distribute new games. Would it be possible to have an (even minimal) mapper onboard?

NeonMan Joined: 24 Sep 2013 Posts: 141	Posted: Wed Oct 12, 2016 12:43 pm
NeonMan Joined: 24 Sep 2013 Posts: 141	A minimal (non SEGA mapper-like) mapper can be done adding just two discrete ICs. I am fairly sure a minimal 1MB SEGA mapper can be done as well with discrete ICs or a mixture of discretes and a fast MCU. I am working on it for a custom cartridge. If I succeed I can port it to the card as well.

NeonMan Joined: 24 Sep 2013 Posts: 141	Posted: Fri Nov 11, 2016 11:04 am
NeonMan Joined: 24 Sep 2013 Posts: 141	Boards arrived! Made the "i am new at this" mistake of making the PCB too close to the card slot width so it does not enter quite as easy at it should (it scratches the slot sides) but a light sanding of the board edges solvers the problem. Mapper testing starts today :D Design using two boards is intentional, the bottom board has the contacts the flash IC and space for a PLD connected to the Address bus and another PLD on the CPU signals, exposing address bus, data bus and many of the signals on the pins where the upper board where the mapper logic itself is implemented. Worst case scenario I'd need to make modifications to the upper board. card.jpg (290.77 KB)

NeonMan Joined: 24 Sep 2013 Posts: 141	Posted: Fri Nov 11, 2016 7:50 pm
NeonMan Joined: 24 Sep 2013 Posts: 141	First test with 32K ROM is working. Card fits nicely on the SMS card slot (see attachment). Will try getting SLOT2 mapping today. IMG_20161111_204012.jpg (2.97 MB)

asynchronous Joined: 14 Aug 2000 Posts: 742 Location: Adelaide, Australia	SegaCard clone Posted: Sun Nov 13, 2016 4:40 am
	Cool. Not a fan of SMD? :)

NeonMan Joined: 24 Sep 2013 Posts: 141	Posted: Sun Nov 13, 2016 4:33 pm
NeonMan Joined: 24 Sep 2013 Posts: 141	IT WORKS! SEGA Card with SEGA mapper but using none of the original hardware (nor any fancy FPGA ;) Marble Madness running off the card slot with SLOT2 mapping! There is still an unknown bug with SLOT1 mapping but is working! Will try fixing SLOT1 any time soon. P.S. Is there any list of SLOT2-Only games? Is this list exhaustive? Quote Not a fan of SMD? Prototyping is easier with DIP, and I _had_ to make some minor hardware fixes ;) IMG_20161113_172757.jpg (2.34 MB)

sverx Joined: 05 Sep 2013 Posts: 3827 Location: Stockholm, Sweden	Posted: Sun Nov 13, 2016 9:05 pm
	NeonMan wrote P.S. Is there any list of SLOT2-Only games? devkitSMS supports only slot 2 thus any ROM bigger than 48KB in the linked list is surely using slot 2 mapper.

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14744 Location: London	Posted: Sun Nov 13, 2016 9:39 pm
	The slot 2 paging list is not exhaustive, lots of games have not been checked.

NeonMan Joined: 24 Sep 2013 Posts: 141	Posted: Sun Nov 13, 2016 11:40 pm
NeonMan Joined: 24 Sep 2013 Posts: 141	I'll probably have SLOT1 fixed in the next days anyway. Meanwhile I've been testing some games on the list. So far I tested "Marble Madness" and "Sonic the Hedgehog 2" with no issue. I am not sure if the Card/Catridge difference would create any issue with certain games. So far these two had no issue.

JomasterII Joined: 11 Sep 2016 Posts: 24	Posted: Tue Nov 15, 2016 12:58 pm
JomasterII Joined: 11 Sep 2016 Posts: 24	My god man. This stuff's amazing. Now we wait and refine until it's as thin as we can get it :)

NeonMan Joined: 24 Sep 2013 Posts: 141	Posted: Mon Dec 26, 2016 11:27 pm
NeonMan Joined: 24 Sep 2013 Posts: 141	Is working! Full SLOT1 / SLOT2 support, works on unmoddified european Master System. Tested it with a known SLOT1 /2 game, ECCO the dolphin, and have had no issue so far. Tested Bubble Bobble as well, which requires a minor patch to work from the Card slot.

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