Harold,

It's the sector erases.

Normally, an excellent way to reduce erase counts would be to write a=20
bunch of 0xFFs, use 0xFF or 0xFFFF as an end of record marker, and add=20
records using writes only.

I tested a few SD cards and I determined that they perform erases at=20
every single write, no matter what data is written. I'm not clear off=20
the top of my head how I determined that, but I was quite convinced at=20
the time. The behavior is probably vendor dependent and unreliable anyway.

.... just one more way SD cards suck for embedded. It's a terrible standard.


Darron


On 4/13/15 8:16 AM, Harold Hallikainen wrote:
>> If you hammer an SD card writing a byte at a time (okay a line at a time=
)
>> then you kill the writes.
> Is there really a problem with writing a byte or line at a time? It seems
> the issue is the number of times a sector gets erased. On several systems
> I've designed, I log to SPI flash. I have a function prototyped like this=
"
>
> UINT32 ExtFlashStreamProgram(UINT32 Addr, UINT8 *pData, UINT32 NumBytes)
>
> This returns the next address that would be written. If a byte is about t=
o
> be written to the first address of a sector, the sector is erased, then
> programmed. My logs typically take several sectors (logging goes to
> everything not used for something else).
>
> So, is the issue the number of write instructions, or is it the number of
> sector erases?
>
> Thanks!
>
> Harold
>
>

--=20
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