Is there a way (and if so what is the best way) to access a memory  
card without a filesystem from Windows (or Linux or Mac)?  Something  
programmatic I'm thinking - so I could just write data to a card with  
a PC with custom software and simply stream it off with a PIC without  
worrying about files or filesystems (or vice versa).

-n.


On Nov 7, 2006, at 2:31 PM, peter green wrote:

>
>
>
>> -----Original Message-----
>> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On  
>> Behalf
>> Of Harold Hallikainen
>> Sent: 07 November 2006 19:03
>> To: Microcontroller discussion list - Public.
>> Subject: RE: [PIC] Interfacing a PIC to a microSD or TransFlash card
>>
>>
>>
>>>
>>>> FAT32 goes up to 32GB in actual implementations
>>> i have a 160 gig fat32 hard drive in an external caddy running  
>>> just fine
>>> with XP, i just had to format it using a win98 box.
>>>
>>
>> Is the "limitation" how many sectors are allowed per cluster?  
>> Microsoft's
>> FAT Overview says BPB_SecPerClus is one byte. Supposedly, for  
>> FAT16 (which
>> is what I'm most familiar with), this could allow 255 sectors per  
>> cluster
>> times 512 bytes per sector times about 65,535 clusters or 8.55e9  
>> bytes per
>> disk. This would be a cluster size of 262,144 bytes. The Microsoft
>> document also says the cluster size must be a power of 2, so the  
>> maximum
>> would then be 128, or 65536 bytes per cluster. It ALSO goes on to  
>> say you
>> cannot have a cluster size greater than 32kBytes.
> IIRC NT allowed you to break that rule and have 64k clusters, I  
> remember the 98 resource kit saying that 98 could read and write  
> fat16 partitions over 2 gigabytes but none of its disk utilities  
> were comaptible with them.
>
>
>> Is FAT32 similar, but with a larger FAT table, and with 32 bit  
>> cluster
>> identifiers in that table?
> i think that is the gist of it but i belive there are some other  
> minor changes too.
>
> according to wikipedia
>
> "In order to overcome the volume size limit of FAT16, while still  
> allowing DOS real-mode code to handle the format without  
> unnecessarily reducing the available conventional memory, Microsoft  
> decided to implement a newer generation of FAT, known as FAT32,  
> with cluster counts held in a 32-bit field, of which 28 bits are  
> currently used."
>
> so that would mean 256 megaclusters
>
> which keeping the 32K cluster size limit would mean 8 terabytes
>
> i don't know why wikipedia says the actual limit is 2 terrabytes  
> and i don't have any ms docs handy to compare but either way its  
> big enough not to be a worry for most hard drives just yet.
>
>
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