Thanks for the reply.
I'm an iPAQ Windows CE user (and developer). Yaffs seems to support Windows
CE so I'm wondering why I might need to use it. I got hold on a Sandisk
spec for a flash part which may or may not be used in their card. It has a
16KB block size. I take this to mean that when writing a 512-byte sector
over the top of an old one that the entire 16KB block needs to be erased.
It would therefore seem that one could write and then delete a 4MB file on a
FAT16 filesystem only 36.6 times before the card is dead due to wearing out
the allocation table block. I hope my understanding about this is wrong,
and was hoping that someone on this list may know the truth. I arrived at
36.6 time by using a 512-byte cluster size, a 16KB erase block size, and
FAT16 filesystem. Since an allocation sector contains 16-bit entries that
chain together clusters it would seem that a full 16KB block would contain
8192 entries which would account for 4MB of storage (8192*(512 byte
clusters)). So, writing and then deleting a 4MB file 36.6 times would cause
300,000 erasures of the allocation block.
Regards,
Steven
-----Original Message-----
From: Charles Manning [
mailto:Charles.Manning@trimble.co.nz]
Sent: Tuesday, 25 February 2003 7:49 AM
To: 'Steven Reddie';
yaffs@toby-churchill.org
Subject: RE: Block size of Sandisk 256MB SD Card
This did get to the list.
I do not know what the block size is. Maybe someone else does. I do not
eeven know if the raw NAND is visible and if it will work with YAFFS.
Why do you want to design with SD? The data is serial and very slow.
SmartMedia is faster. If size is a factor, then maybe XD (the next gen
SmartMedia) would be better.
I'll be interested in what you find out.
-- CHarles
-----Original Message-----
From: Steven Reddie [
mailto:smr@essemer.com.au]
Sent: Friday, 21 February 2003 7:01 p.m.
To:
yaffs@toby-churchill.org
Subject: Block size of Sandisk 256MB SD Card
Hi, I'm very much a flash newbie having just got a Sandisk 256MB SD card
yesterday to use in an iPAQ. My programming experience includes FAT file
systems in a fair bit of detail. Does anyone know the size of an eraseable
block on this? Is the unit for such a block known as the sector?
Regards,
Steven
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