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 Robotics / NXT / 133
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Subject: 
Re: Flash Write Cycles
Newsgroups: 
lugnet.robotics.nxt
Date: 
Tue, 12 Sep 2006 13:49:46 GMT
Viewed: 
14139 times
  
In lugnet.robotics.nxt, <dickswan@sbcglobal.net> wrote:

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".

[...]
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.

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 SAM-BA is loaded into flash memory it unlocks the first two pages of flash
memory and then it relocks those two pages.  When you then download a firmware
to the NXT the first two pages of flash are unlocked and they remain unlocked.
So each firmware download results in a cycle which changes the lock bit state
from unlocked to locked and then from locked to unlocked.  If the cycle limit is
7500 cycles then it probably isn't a big deal  It would be a huge deal if they
failed after 100 cycles.

If they ever do fail in the locked state then you would have a permanently
clicking brick.

John Hansen



Message has 1 Reply:
  Re: Flash Write Cycles
 
(...) flash Are you sure of this John? It seems like the reset button would be for dire circumstances and would do something different than the firmware boot mode. The spec says this about SAMBA loading: "To enter SAM-BA Boot Recovery, the TST pin (...) (18 years ago, 13-Sep-06, to lugnet.robotics.nxt)

Message is in Reply To:
  RE: Flash Write Cycles
 
(...) 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 (...) (18 years ago, 12-Sep-06, to lugnet.robotics.nxt)

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