~ OPENSOURCE USB CARTRIGE DEVELOPMENT ~

HardWareMan · Post by **HardWareMan** » Thu Jan 24, 2008 6:58 pm

Jorge Nuno wrote:Quick question:
How long does reading a whole 512byte sector from a SD/MMC takes?
(Just 1 sector)

Maximum theoretical speed is 33MHz of clock signal or 33Mbits (info from datasheet). But not all cards can handle that. And bus cycle are more complex. You can use MMC+ or even SD interface (wich 8 bit - 8x times faster), but not enough just feed data to M68K. Many other hardware sometimes use the cartrige resources: VDP, Z80. Of course, bus cycle will be converted to standard M68K bus cycle, but with differ timings. My test with DRAM not works. I even try to use pure NAND chip....

Jorge Nuno · Post by **Jorge Nuno** » Thu Jan 24, 2008 7:06 pm

I was thinking on SPI mode only: data in, data out, sericlock

It takes 8 clock cycles to transfer 1byte (in SPI)? Or is it like DDR? Data transfer on both rising and falling edges of the clock signal?

Can I access directly a sector? Like:
"Give me sector 0"...

HardWareMan · Post by **HardWareMan** » Thu Jan 24, 2008 7:12 pm

Use this. All what you need.

Jorge Nuno · Post by **Jorge Nuno** » Thu Jan 24, 2008 7:50 pm

Woot thanks for the link

http://www.alldatasheet.com/datasheet-p ... 2SA00.html

^ in page 22 it says that the maximum clock frequency, in data transfer mode is 52MHz... But I don't think that speed is enough for the 68K in SPI mode...

Chilly Willy · Post by **Chilly Willy** » Thu Jan 24, 2008 11:04 pm

HardWareMan wrote: While you dreaming about it, I have gathered a prototype. Yes, there is a small flash memory with the loader, 4 Mbytes RAM (actually it's a PSRAM - Pseudo Static RAM, dynamic RAM have not compatible interface and need to be regenerated, pseudo SRAM do this internally at background and have SRAM bus interface) and port for the SD / MMC card.

Cool! Using PSRAM is mostly a given - it's easier than DRAM and cheaper than "true" SRAM. Does it have an FPGA? I'd buy one if you could put it together. Most of my hardware is still packed away. I currently can't do much more than soldering at the moment.

By the way, I love that link you posted for the SD/MMC cards.

tinctu · Post by **tinctu** » Fri Jan 25, 2008 10:21 am

@HardWareMan->
But SegaIDE need lot of hardware mods /wires/...
So You must mod console...
/But maybe better solution as cartrige.../

Can it be as standalone interface for CD connector???

HardWareMan · Post by **HardWareMan** » Fri Jan 25, 2008 1:07 pm

tinctu wrote:@HardWareMan->
But SegaIDE need lot of hardware mods /wires/...
So You must mod console...
/But maybe better solution as cartrige.../
Can it be as standalone interface for CD connector???

There no need to mod the console to use my SegaIDE. Every console with SegaCD connector can work with it. And SegaCD have an "!ROM" signal, wich active when cartrige slot is empty. But you are will be limited by 17 addresses lines (or 256Kbytes) for Boot ROM. But, with supporting by big storage (SD/MMC or even HDD) it does not matter - you can load needed runtime code in console RAM. 64Kbytes will enough for your task.

tinctu · Post by **tinctu** » Fri Jan 25, 2008 4:28 pm

So geeks ->

1./ USB+SD-CARD cartrige

or

2./ Sega MEGADRIVE/GENESIS-IDE+CF-Adapter

???

Vote please!

HardWareMan · Post by **HardWareMan** » Fri Jan 25, 2008 4:41 pm

1,5./ Sega MEGADRIVE/GENESIS-SD/MMC Adapter %)

Chilly Willy · Post by **Chilly Willy** » Sat Jan 26, 2008 5:52 am

tinctu wrote:So geeks ->

1./ USB+SD-CARD cartrige

or

2./ Sega MEGADRIVE/GENESIS-IDE+CF-Adapter

???

Vote please!

I think 1 is a little better as many people already have CDs and 32Xs in place, and swapping to the IDE adapter and back would be a pain. The USB/PSRAM/SD-CARD cart is better for people in that respect - just plug it in the cart slot and you're done.

HardWareMan · Post by **HardWareMan** » Sat Jan 26, 2008 6:19 am

Hint: There are no need in USB, when you using BROM/PSRAM/SD-MMC cartridge. But when you need to transmit some SYNC signals - you can use MD joystick port.

LocalH · Post by **LocalH** » Sat Jan 26, 2008 6:41 am

All this talk of 4MB...seems either noone read or noone cared about my idea. I'm not suggesting that all carts have 32MB of buffer that most people won't use, just that the design can support it such that a higher-cost cart can be made with full SSF2 banking support.

HardWareMan · Post by **HardWareMan** » Sat Jan 26, 2008 9:05 am

Well, then you need to mark all the technical specifications of the project.
If the cartridge is not designed to run ROMs, then no need put 4 Mbytes buffer. Use only RAM in console or add a small buffer if necessary. Boot ROM will just have to put to the work with MMC/SD. But USB, IMHO, is not needed. To connect with other devices you can use joystick port - it contains even UART (with some limitations).

tinctu · Post by **tinctu** » Sat Jan 26, 2008 6:59 pm

So simple JOY-PC cable for data transfer???
But I mean mini-USB for those ,they have no SD-card reader...
And modern PCs/notebooks have no LPT...

Well than stay in concept v2...

- white PCB
- blue LED /PC-data,SEGA-read/
- cartrige /MD,GENNY,32X,NOMAD compatible/
- Battery RAM+Battery
- FGPA
- SD-CARD / MMC-CARD
- PIC or ATMEL /USB+ROM/???
- mini-USB /for PC-CARTRIGE data transfer -> cart will be not pluged in SEGA.../
- plastic case /I choose transparent one - cheaper material/
- www with full documentation
- enable *.ROM /SMD/ and *.BIN
- build in *.TFM player

it will be long long long way...

PS ->So next month i will post very first 3d models for case design...
And You will correct (very first) dimensions /-> PCB etc/...
So stay in touch.Bring new ideas... and fresh solutions.
I will be offline...

(I have some very important things on work this days...)

Jorge Nuno · Post by **Jorge Nuno** » Sat Jan 26, 2008 8:18 pm

A SD/MMC card will not feed the 68K with vaild data in a 68K clock cycle:

Command: 8clocks;
Argument: 32clocks;
CRC: 8clocks;

Response time: 8clocks (worst case);
ACK Response: 8clocks

Total: 64 clocks... Even if the card is working @ 50MHz, It isn't enough...

Because for every 68K clock cycle there are only 6 50MHz cycles

^Thats just for the card to begin transfering actual data

Then there are more 515 clocks to transfer a whole 512 byte sector

Blehh it must have a RAM buffer to put the whole ROM inside it, like 8MB... I think DRAM is the best one...