On 3 Jun 2006 00:49:43 GMT, Arno Wagner put finger to
keyboard and composed:

In comp.sys.ibm.pc.hardware.storage Franc Zabkar wrote:
On 1 Jun 2006 20:25:19 -0700, put finger to
keyboard and composed:


Franc Zabkar wrote:

On 31 May 2006 16:27:03 -0700, put finger to
keyboard and composed:

I have a USB thumb drive that my computers can read but can't write.

This device uses an OTI 6828 USB bridge chip and was distributed by
Pretec as the iDisk and also given out by Microsoft years ago (they
have nothing on it), but I can't find any information about it.

The OTI chip has a Flash Write Protect signal on pin 18
(http://www.costar.com.tw/pdf/OTi/Oti-6828.pdf). Have you verified
that it changes state according to the position of the read-only
switch?

Have you tried to format the drive? Is it possible that the directory
you are trying to write to has a read-only attribute???

Thank you, Frank. That's great in formation. I'll take a look at pin
18.

I had no luck formatting the drive, and nothing had the read-only
attribute enabled.

IIRC, someone with a similar problem found that there was a limit to
the number of files you could have in the drive's root directory.

That is a FAT limitation: All directories expand as needed,
except the root directory. You should still be able to rename
files and directories there and you should be able to write
in subdirectories. (The limitation is a design error IMO.)

But
this doesn't explain your inability to format the drive ...

What about this: The drive has exhausted its supply of spare
sectors and goes into a safe read-only mode now. Would be a sensible
failure mode, because the user can at least get his/her data of
the drive and there is no risk of failed writes.

Arno

But if the user requested a format, wouldn't that tell the drive's
smarts that the data wasn't of any consequence?

- Franc Zabkar
--
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