The SIO2SD of Lotharek is the Floppy Disk Drive emulator for the Atari home computers.
I got it with my Atari 800XL.
Information:
https://lotharek.pl/productdetail.php?id=60
https://www.classic-computers.org.nz/blog/2015-06-13-sio2sd-for-atari.htm
http://sio2sd.gucio.pl/wiki/English