05-07-2012, 04:26 PM
Having implemented SD card reading on 65C816 and Z80-based systems, I'd say the crucial point would be to find a C compiler that can compile FF or PFF (FAT parsing library). You could certainly rewrite PFF in assembly, but it only takes a quick glance at the code to see why that would suck 
The low level SD card I/O code that sends MMC commands and reads sector data could be done mostly in C except for the most performance-critical parts (though I've used assembly exclusively in my implementations).
The low level SD card I/O code that sends MMC commands and reads sector data could be done mostly in C except for the most performance-critical parts (though I've used assembly exclusively in my implementations).