Subject:
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RE: Flash Write Cycles
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Newsgroups:
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lugnet.robotics.nxt
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Date:
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Tue, 12 Sep 2006 04:28:49 GMT
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Reply-To:
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<DICKSWAN@SBCGLOBALspamless.NET>
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Viewed:
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13422 times
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> > John Hansen on September 11, 2006 10:58 PM wrote:
> >
> > I could write a little test program which would repeatedly boot
> > the brick into firmware download mode, download the firmware, then
> > repeat if anyone would like to see how many times it can go through
> > that cycle before the lock bits quit working.
I guess it depends on which way they fail? Do they fail in locked mode
or in unlocked mode? If, as would be good design, they fail to
permanently locked, I'd guess nobody is interested in trying.
What nobody has mentioned yet is the following:
After downloading firmware, the lock bits are left in unlocked mode.
This is good.
I strongly suspect that erasing locked bits that are already erased
doesn't count in the count of "how many times can I erase this".
This is based on 25-year old knowledge from building a bit-banged flash
erase and programmer for first generation EPROMS. With these you pulsed
the flash erase line while applying 12V power. To do a single "erase"
pulse. To erase a flash sector you sent one erase pulse and then checked
to see if everything was erased. If not you continued looping. When
flash was new it might only take 5 to 10 times through the loop. As it
aged with more erases, it took more pulses to do a erase. When you
reached 50 to 80 erase pulses you discarded the flash because it was
worn out.
Modern flash have the erase built-in and I'm sure use a different
technology. But I expect the keep pulsing until erased may still be
valid.
So I suspect if locked bits are already erased there is no "strain" on
the contents if you do another "erase". If this is the case, exceeding
write cycles on "lock bits" is not an issue.
Hopefully, there are more knowledgeable and up-to-date hardware
designers who may want to comment.
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Message has 1 Reply:
 | | Re: Flash Write Cycles
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| (...) [...] (...) According to what I have read, putting the AT91SAM7S processor in system recovery mode (i.e., by resetting it via the hardware reset button or by programmatically putting it into firmware boot mode) loads SAM-BA into flash and when (...) (18 years ago, 12-Sep-06, to lugnet.robotics.nxt)
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Message is in Reply To:
| | Re: Flash Write Cycles
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| (...) Whether you reset the brick or just run the download firmware routine in the LEGO Mindstorms NXT software or in RobotC or in NBC/BricxCC you've put the brick in SAMBA mode (clicking brick mode) and the lock bits have been cycled. But I have (...) (18 years ago, 12-Sep-06, to lugnet.robotics.nxt)
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