'morning,

I've found numerous articles discussing how to emulate a floppy disk 
DRIVE, here and elsewehere and there even seem to exist commerial 
solutions.

Yesterday I revived an old SB180FX (HD64180 CPU with a CP/M compatible 
OS) and had been contemplating beforehand what to do if the floppy 
drives or the disks failed. I was wondering if it were possible to 
replace the floppy controller (FDC9266) by a microcontroller that 
emulated the FDC (register read/write, DMA) and stored the data blocks 
on an SD card or such (anyone know if SD cards with 1.44MB capacity 
exist? ;-) ).
I would read/write the raw data on my PC, so the controller would just 
map the floppy's blocks 1:1 to the SD card or even map all four drives 
to separate sections on the SD card.

The bus speed to the processor (running a ~12MHz) would need some 
attention, maybe adding hardware support in the form of a flipflop which 
generates WAIT cycles (within reasonable limits) by being set 
automatically by any access and which is then reset by the 
microcontroller. This only affects the reading/writing of commands and 
status, after that the microcontroller would work internally 
transferring data via (emulated) DMA.

I'd prefer an ATmega of sorts.

Question: has anyone done this before?

Josef

Use such one:
https://www.amazon.de/Inch-USB-Floppy-Drive-Emulator/dp/B0083Z29JO

http://hxc2001.free.fr/floppy_drive_emulator/index.html#SDCARDFloppyemulator