Controllers in SD/MMC cards

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[NB: this split from a thread in AVR Forum about formatting SD/MMC cards]

clawson wrote:
SD/MMC have an ARM on board

Oh, that's very unlikely. A '51, usually.

JW

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Quote:

clawson wrote:
SD/MMC have an ARM on board
Oh, that's very unlikely. A '51, usually.


NOW we can get our teeth into something. ;)

Before trying to investigate, I'd think most '51 would be crippled with today's densities for address lines. I'll guess with Cliff. Now to see if Google will help...

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Why would the controller deal with memory addresses? The data are moved all by hardware.

The main issue with ARM are the royalties.

JW

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No they are ARMs - ARM7's in fact - there's been lengthy discussion about this previously. In fact this is one of the things that really helps to inflate ARM deployment numbers. Apparently it's something seriously sub-$1 per unit.

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Quote:

Why would the controller deal with memory addresses?

??? Now you've lost me. I thought that memory cards (and "USB sticks") are conceptually a bank of dataflash chips. (In practice they may not be "chips", right?) So wouldn't the controller need to access these with an address and/or data bus?

Quote:

you don't want to write sectors needlessly. It's true SD/MMC have an ARM on board that does wear levelling and bad sector remapping but you still don't want to wear sectors in the flash array needlessly.


Tell that to ReadyBoost... :twisted:

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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A couple of examples with the '51:
http://www.phison.com/upload/edi... (have a look at the picture)
http://www.alcormicro.com/en_con...

Any link to an ARM-based SD card controller?

theusch wrote:
Quote:

Why would the controller deal with memory addresses?

??? Now you've lost me. I thought that memory cards (and "USB sticks") are conceptually a bank of dataflash chips. (In practice they may not be "chips", right?) So wouldn't the controller need to access these with an address and/or data bus?

There is a specialized hardware which performs the heavy lifting - reads/writes to/from the FLASH, and also the reads/writes to/from the SD interface (which is exposed to the outer word). And there is a hardware which performs the ECC needed for the NAND FLASH chips (yes, they are chips - well, depending on the definition of "chips", of course ;-) ). So the bulk of the data does not need to go through the embedded processor core.

JW

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LOL...
Quote:
Embedded RISC architecture 8051

Even x51 are RISCy nowadays it seems. ;)

The ball has gone over the net, and is now in Cliff's court...

Lee

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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I have a distant memory of a controller made by Genesys perhaps?

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Quote:

Any link to an ARM-based SD card controller?

I can't tell if this device is equivalent/similar to what you posted or not:
http://www.arm.com/community/par...

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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Quote:

equivalent/similar

It's a host controller. Surely something you plug an SD/MMC into rather than something you build into an SD/MMC?

PS I found a datasheet for a Genesys GL424 which mentions "RISC core" and has an internal 1.8V regulator which might suggest an ARM core but nothing concrete.

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Lee wrote:
Quote:
Embedded RISC architecture 8051

Even x51 are RISCy nowadays it seems. ;)
That's the usual way how the far-easterner label the single-clocker '51s.

clawson wrote:
PS I found a datasheet for a Genesys GL424 which mentions "RISC core" and has an internal 1.8V regulator which might suggest an ARM core but nothing concrete.
The low supply voltage is the consequence of the small transistor geometry (0.18um) and does not imply the core. It's most probably not a '51 in this case, as the Genesys USB FLASH chips' datasheets do say it has a '51 core; nevertheless I doubt it's an ARM, I even doubt it's anything more than an 8-bitter - they would probably proudly say if it would.

JW

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Well a bit more research says that a big player in the SD/MMC game is http://www.skymedi.com.tw with a lot of cards previously using their SK6602 and SK6612 devices though these now seem to have been supplanted by SK6617: http://www.skymedi.com.tw/englis... however there's no clues as to the core or any sign of datasheets etc.

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Well, I don't doubt there are 32-bit cores in the game, especially at the high-end players; and maybe also ARMs although I doubt the latter (both parties would probably proudly say it out aloud). I just say that the commonplace cheap variety simply does not need the horsepower so nobody throws out the money for the horses.

But now I feel guilty for derailing this thread. Could you please cut the OT part off, Cliff/Moderator? Thanks.

Jan

PS. Try to have a look at SK6602 ;-)

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Quote:

But now I feel guilty for derailing this thread.

lol -- it is OK with me. It is something I never really thought about before, and surprising to me quick Google searches didn't uncover many gory details about the card innards.

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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The interesting part of these chips is the fact these access NAND flash and do not have the on-board program memory, so I guess the NAND must come pre-programmed with a bootloader (there is a firmware upgrade option available) and some kind of NAND interface which does stuck bits recovery for the bootloader. Usually bootloader and firmware eats up several kB of the card.
Some NAND flash chips are sold with error-free 0-th flash page (the one I have from Samsung), so in this case the recovery of a program memory is not critical(could be made in software).

Lets face it - most of these chips support below 50MHz serial clock, which means a throughput of < 50/8=6MB/s (with 1bit interface). That is a job for ATTiny2313 with some dumb additional hardware, not for 32-bit ARM. The high level algorithm is mainly the wear-leveling I guess.

And the last thing. Have you ever heard about xD memory cards from Olympus?
http://en.wikipedia.org/wiki/XD-Picture_Card
These are not flash cards actually, but bare die flash chips. If anyone would like to play with a low level NAND flash access - this is a good choice because of the huge pin spacing (when compared with bga256).

No RSTDISBL, no fun!

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I found the reference for SD card controller built on ARM7
http://www.bunniestudios.com/blo...
The chip marking is S3C49VDX. I couldn't find a datasheet but as googling for S3C49 returned several NAND-FLASH interfaced devices (including MMC controllers) built around the ARM, it makes sense.

As it appears that Samsung does use these controllers only in their own SD cards and don't sell them to the "cardmaker public" (there is no mention of controllers on their pages), it makes sense that they don't advertise. They are also one of the biggest (if not THE biggest) ARM licencee, so the royalties for them might be quite low indeed.

JW

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Quote:

it makes sense that they don't advertise.

True enough, but as several places etch off the top of Mega168 and other chips, you'd think a simple search would uncover at least a picture of the innards. Not that we could tell what type of micro core is being used.

[What are those sites again that have explored the innards of microcontrollers and other chips?]

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.