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Repo MVS Cart PCB Discussion

Fluffy

Fluffy

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twistedsymphony said:
We need cart PCBs like the PGM ones so we can make carts out of games like this!
Click to expand...
I did make a start on laying out the char board. The problem is that you can fit max 8 x 27c322 onto a board, and then the space is tight for fix, sound and a small CPLD for de-multiplexing and banking. If you use larger flash chips you may need programming logic as well, and at some point the design is so expensive that it'll be easier to just buy an existing flash cart.

Edit:
https://wiki.neogeodev.org/index.php?title=CHA_board
Are there many games that require more than 8x4MB, or the advanced fix banking?

Edit2:
Downloaded teot.zip, it requires 64MB C-ROM (assuming they didn't just pad it to that size).
 
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That's true, but most of these game max out the V-ROM space before the C-ROM space

I think just PROG Repo board that could use 4x 322s for V-ROMs an 1x322 for P-ROM would go a long way

for the CHA board a straight Repo of the 512Y or 256 board variants would be great for use of 322s, but then a new version that supports 64Mbit or larger SOP44 ROMs with a 3.3V converter and some level shifters would be a great way to support the games that need the larger C-ROM space.
 
PROG shouldn't be too hard, furrtek has some Verilog description for the V ROM multiplexing, and you can probably do the P ROM banking with a GAL.

I am a bit reluctant to design with SOP chips, as they are harder to solder and program, which is a barrier for many people to use them. Of course, most modern Flash are TSOP or BGA, which are even harder.

Edit:
I don't think NEO-ZMC is possible as a GAL, so would need a small CPLD. Or you'll have to have to design the audio driver to use only a single zone, so homebrew-only.
The NEO-273 can be done as discrete logic, though that will take up quite some space. Or move to SMD, which would make soldering harder.
NEO-CMC would require a small FPGA.
 
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They do make SOP44 sockets:
Hc37b734789024277820d680d84f1f0b1a.jpg


I've seen plenty of repo NEO-ZMCs out of china so those are likely available somewhere, as the 273 and PCM Furrtek makes drop-in replacements: https://www.tindie.com/stores/furrtek/
 
Ok, that is cool and I didn't know that.

Though Furrtek's replacements are probably more useful for repairs, in a custom PCB you can use those chips directly.
 
On a custom PCB you can do those chips on TTL.

Go check out MVS scans @ stuff like lansqunet 2004 and some of the KOF bootlegs / hacks.
(on lansqunet the "ACTEL" is used for program decryption. only i think..)
 
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Ok, I'll have to see when I have some time to look into this and finish the layouts. I am not going to object if anyone else wants to do it, because right now I don't have much more than the rough schematic.
 
Well, the basic layout is needed first anyway and then the customs / repro's / TTL's is separate and added in when available.

I have been looking for lans. 2004 for some time for the customs with no luck :/

"set 7" on this page also has another one in TTL, however still use a ZMC.
https://www.mvs-scans.com/index.php/Bust-A-Move_(pirate)
 
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from the look of that diagram the ZMC is nothing more than a tiny RAM chip; or am I missing something?
 
how fast does it need to run? anybody put a scope or frequency counter on one?
reason: i like to use microcontrollers for things other people would use a pld for.
 
I guess it depends on the clock speed of the Z80. I think it takes 4 bus cycles for an instruction to execute, so I guess clock speed / 4?

Edit: Scratch that, data is read at the end of T2, so it needs to complete in the time for that. Normal read/write are 3 bus cycles. Also you need to consider the time for the ROM to return a value.
 
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well an stm32 can clock at about 100MHz - so should be fast enough.
5v tollerent pins on those, so just add 5v pullup resistors if needed (probably not needed)
 
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