4 Dec
2010
4 Dec
'10
12:31 p.m.
On 4 Dec 2010 at 19:33, Tony Duell wrote:
As far as I know, there is nothing in the SCSI spec
that specifies a
minimum data rate or a maximum seek time. Soyou could even read 1 byte
out of an SD card and then send it over the SCSI interfce, and then do
the net byte, and so on. It would probably be better to buffer a
'sector' in RAM on the microcontroller, and then transfer the buffer
to the SCSI interface.
There's an excellent argument for heavily cache-ing SD card accesses
when using it as a hard disk--to minimize repeated writes to a block
(usually 16K) of SDRAM to extend longevity of the medium--and to
defer much slower writes as much as possible for performance reasons.
If reading speed was an issue, one could employ the faster 4-bit
access to SD rather than the simpler and much slower SPI mode that's
usually used for slow embedded applications.
--Chuck