OTP Secure Digital ?

I am looking for SD (Secure Digital) memory that can be programmed only once. Basically, once programmed, it cannot be erased. I searched the web, but I did not find any. Please let me know if you are aware of such technology. Thanks.

T.I.

Reply to
Talal Itani
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There is no such thing.

Mass-produced removable memories like this tend to use mask ROM. If they resemble SD it's only cosmetically. Such devices have a vested interest in NOT using a simple-to-duplicate storage format where blank media are available off the shelf.

Reply to
larwe

There are such things as OTP devices; we call them PROMs :)

Cheers

PeteS

Reply to
PeteS

Multimedia cards have a permanent write flag in the CSD register. I have not tried this feature but from a data sheet I have, it permanently disables erases + writes. Not sure if SD card has the same functionality - I don't have a technical spec for one of those.

Regards,

Paul.

Reply to
Paul Taylor

Used to be lots of them. They contained fusible links which, once blown, can't be unblown.

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Reply to
CBFalconer

The CSD register of the SD interface contains a write-once bit called PERM_WRITE_PROTECT that does the follow (quoting) "Permanently protects the entire card content against overwriting or erasing (all write and erase commands for this card are permanently disabled). The default value is 0, i.e. not permanently write protected."

Peter

Reply to
Peter Dickerson

The OP appears to be making something like those sewing machines or fitness trainers that use removable media cards to store software packs (stitch patterns, exercise programs, etc). SD is really not the right choice for an application like this; even though many such devices LOOK like SD cards, they almost never are.

The write-protect bit to which you refer can be subverted by various means.

Reply to
larwe

Can you explian what you are trying to use this for, and how secure, and how large, the OTP aspect needs to be.

Is it to prevent accidental corruption, or does this hold unique IDs that must remain secure, or is it a high revenue/high volume product you want to protect from rampant cloning (or virus/tampering) ?

-jg

Reply to
Jim Granville

Hi Jim,

I am trying to keep people from accidentally erasing the contents of the microSD. Basically, once it is programmed, I want the data to remain there, and not erased or programmed again. This is for a product, yet not a mass produced product. The size I need is 512MB. The microSD will not hold unique ids. Thanks.

T.I.

Reply to
Talal Itani

Thank you very much. This is exactly what I am looking for.

Reply to
Talal Itani

Is that an actual SD data sheet, and not a MMC data sheet? If it's an SD data sheet, how did you get it - did you pay for it or find it on the internet? If you got it off the internet, a link would be appreciated.

Regards,

Paul.

Reply to
Paul Taylor

Hi Peter,

Thank you for this information. To write the microSD cards I have been using USB card readers, under Microsoft XP. That setup does not give me access to the bit you are referring to. I'm I missing something? Do you know of tools that allow me to manipulate the bits of the CSD register? If I write my own software under XP, will I have access to that register? I hesitated to trouble you again, but you gave me a clear answer to my initial question. Thanks a bunch.

T.I.

Reply to
Talal Itani

You need to use CM27 (PROGRAM_CSD). Presumably you can control the hardware under XP with a device driver, but it will be a big job for a small task, and hardware dependent. Whay don't you get the target hardware to do it?

Peter

Reply to
Peter Dickerson

Windows XP writes and reads SD and microSD, so device drivers should be there already, somewhere in XP, maybe I am wrong. I do not understand why you say that I need device drivers. You asked me: "Why don't you get the target hardware to do it?" By target hardware, do you mean the card reader I attach to the PC through USB?

Reply to
Talal Itani

"SanDisk" now has exactly what you described:

formatting link
SanDisk® 3D-OTP SD ROM Cards (Effectiverly SD-PROM, write-once SD-card).

web,

Reply to
Yuri

Regular SD cards also have two bits (bits 12 and 13 in the CSD register) called TMP_WRITE_PROTECT and PERM_WRITE_PROTECT. There is also command 28 SET_WRITE_PROT which sets up a separate set of write protection groups.

I can't say for sure if EVERY brand of SD card supports these features, however based on the handful of cards that I tested, the write protection features do work. Once a card is protected, a standard card reader connected to a Windows PC can't change the contents. Unfortunately most card readers don't recognize internal write protection the same way they recognize the little plastic tab on the side of the card. If the plastic tab is moved towards the "locked" position, Windows will tell you "your disk is write protected". If you protect the card using command 28, Windows remains oblivious to this fact and lets you copy and delete files as much as you want, when in fact you're not actually changing anything on the card.

Perhaps there are card readers that handle this properly, but the one that's sitting on my desk right now (using a Genesys GL816E chip) does not. I imagine you will run into the same problem with the Sandisk SD-ROM card.

Reply to
Tom

Sure there is. Not called "SD (Secure Digital)", though. An old fashioned EPROM. The fusiable link variety, not the EEPROM variety. Once you blow the links, it's pretty hard to change. Not very fast in access time, though.

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Reply to
ArarghMail802NOSPAM

A simpler method is the old fashioned EEPROM with no quartz window. Program it once only.

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Reply to
CBFalconer

There's no such thing. There were fusible-link PROMs, and there were (are) EPROMs, but they are two different things.

Some kinds of fusible-link PROMs, notably the early type with nichrome fuses, tended to have a problem with fuse regrowth. In a sense, the PROM could be said to self-erase, over a very long period and not in a reliable way. It was not possible to erase them electrically or through the use of ultraviolet light.

Most fusible-link PROM vendors changed to other fuse materials such as titanium-tungsten at least in part to reduce the regrowth problem.

Fusible-link PROMs have been obsolete for some time now; no mainstream semiconductor manufacturer still makes them. For some applications, they were replaced by OTP EPROMs, which are simply EPROMs in packages that are not transmissive to UV light, hence not erasable. These are less expensive to manufacture than EPROMs in packages with quartz windows.

There were some attempts to make EPROMs in all-plastic packages, usually with a window of a different type of plastic than the main body. These were erasable a small number of times, as the plastic tended to become opaque to UV with extended exposure.

Eric

Reply to
Eric Smith

When I mentioned this some years previoiusly in another newsgroup, I was told that it had never been done, despite that I have in my posession some production EPROMs of this type. Although it doesn't prove that SGS used the technique in production, they were issued U.S. Patent 4,971,930 for a method for encapsulating chips in plastic packages with plastic windows tranmissive to UV.

Obviously such a technique is of little practical value today, since flash memory has almost entirely replaced EPROM.

Reply to
Eric Smith

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