4 Dec
2010
4 Dec
'10
2:56 p.m.
On 4 Dec 2010 at 18:50, Alexandre Souza - Listas wrote:
Speed Class Rating
The Speed Class Rating is the official unit of speed measurement for
SD Cards, defined by the SD Association. The Class number represents a
multiple of 8 Mb/s (1 MB/s), and meets the least sustained write
speeds for a card in a fragmented state.
Using SPI, 400KB/sec is about the top rate for read, 200KB/sec for
write. If you can get 1MB/sec write speed, more power to you. Most
uC implementations get substantially less.
Most first-timers trying to wring performance using SPI out of an
SDHC are surprised by the low transfer rate.
Cache-ing would help a lot.
--Chuck