[Coco] Creating /d1 descriptor for 2nd floppy?

[Christopher Barnett Fox]

Good morning!

I'll expose my forgotten knowledge here... I have some old OS-9 Lvl II
boot disks that already have a working /d1 device descriptor that I can
use to access a second DSDD 40-track floppy drive. I have some others that
don't have the /d1 descriptor.

What's the process to create the descriptor? I have the old Rainbow guides
to OS-9 and OS-9 Lvl II, but can't seem to find any documentation there. I
see references to tmode?

Thanks!

Christopher