gnupic: flash filesystem for pic and 24xxx EEPROMs?
Subject:
Re: flash filesystem for pic and 24xxx EEPROMs?
From:
Bernd Oefinger ####@####.####
Date:
7 Jan 2005 12:41:47 +0000
Message-Id: <200501071341.43087.bernd@oefinger.de>
Am Freitag, 7. Januar 2005 10:00 schrieb Vangelis Rokas:
> ----- Original Message -----
> From: "David McNab" ####@####.####
> To: "Vangelis Rokas" ####@####.####
> Subject: Re: flash filesystem for pic and 24xxx EEPROMs?
> [snip]
> > Some basic requirements that come to mind are:
> > 1) wear-leveling - the only tolerable type of failure is an
> > 'out of space' error
>
> I still can't understand what do you mean with 'wear-leveling'!
The problem with flash, EEPROM etc. is that it can only be written
a limited number of times per cell/sector/byte (whatever unit). Traditional
filesystems often use a fixed location for filesystem information data
(e.g. the FAT). This leads to the problem that those (fixed) locations
are written n-times more often than all other locations of the memory.
Therefore the memory may be "worn out" (=> unusable because the
first locations cannot be written anymore) far too early compared to
a filesystem that takes care of this fact and uses no fixed locations for
management information (=> wear-leveling).
Modern flash filesystems e.g. those used by Linux take care of this
problem. Unfortulately they are much too complex to be ported to PIC.
The only thing that may be ported is the "idea" behind the algorithms.
Regards,
Bernd
