FAT table MMC/SD durable when logging in SPI mode

Jimmy Lee · Guest

Hi,
I have a data logging project with MMC/SD card using SPI mode with FAT16. The block is set to 512 bytes. On average, one block of data will be logged on the card for every minute.
Is true that, each block of data writing into the card, the FAT16 table will be updated? if this is true, then the FAT table will burn out very soon, about 70 days ( assume that 100 000 write-cycles for MMC/SD card).

Is there a way we can prolong the durability of the FAT table on the card?

Can anyone commment on this?

Thank you in advance,
Jimmy

ckielstra · Joined: 18 Mar 2004 Posts: 3680 Location: The Netherlands

When and how often the FAT16 table is updated will depend on your FAT16 driver. You didn't mention who is the supplier of your FAT16 driver so there is no way we can tell something about it's behaviour.

A general working trick to avoid the updates to the FAT16 table is to create one or more very large files just once. Following updates to the contents of these files will not affect the FAT16 table as long as you don't change the size of the files.

Guest · Posted: Tue Sep 26, 2006 12:04 am

Hi,
I got the FAT16 MMC/SD driver from Progressive Resources LLC.
Thank for your reply.
Jimmy

asmallri · Joined: 12 Aug 2004 Posts: 1630 Location: Perth, Australia

Don't forget SD cards implement "wear leveling" swapping out dud blocks. If you are only performing heaving writing on a small area, as opposed to over the entire media, then wear leveling will increase the effective endurance.
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