On 5 Dec 2010 at 2:08, Phill Harvey-Smith wrote:
Comments & sugestions welcome.
Use an ARM CPU. The SD-to-CPU connection is straightforward and you
should have more than enough I/O pins to implement the 4-bit
interface. Since most ARMs have internal PLL clock generators,
getting 60-70 MHz is easy on all but the lowest-end models.
SCSI bus drivers should be OC, not totem-pole (so you can have more
than one device on the bus), so you'll want to use something like an
LS641 for the bus transceiver. You can do active termination with a
2.85V LDO regulator (I like the LM1086) and some 110 ohm resistor
packs.
Many ARMs have built-in external RAM controllers, so adding a few MB
of RAM for cache is easy. Some offer DMA.
--Chuck
P.S. I'm looking forward to Energy Micro's Giant Gecko line with 128K
of RAM on-chip.