Connect Schneider CPC 3" FDD (A:) to PC as B: 
(connect to straight part of ribbon cable, 
FDD A: remains after the twist)

PC Pin <-> 3" Pin
1-6 <-> n.c.
7-8 (Index) <-> 1-2 (Index)
9-10 (Motor A) <-> n.c.
n.c. <-> 5-6
11-12 (Drive Select B) <-> 7-8 (Motor on?)
13-14 (Drive Select A) <-> n.c.
15-16 (Motor Enable B) <-> 3-4 (Drive Select 0?)
17-34 <-> 9-26

Accessing the 3" FDD works in MSDOS on slower PCs (up to Pentium II/III),
the drive can be handled as 5.25"/360 KB drive in the BIOS.
My Athlon 1.2 GHz has timing problems when writing/reading in MSDOS. 
However, formatting works and floppy images can be transferred using Imagedisk.