(Okay, I may be cheating...it was a toss up as to whether this should have gone in the Off Topic forum :-) )
One of the jobs I have where I work is the 'setup' of embedded PC's (basically a PC on a 3/4 EISA size pc board). The setup consists of using 5 floppies to load the CMOS settings and our program code. You can imagine how boring it is just setting there waiting for one floppy to finish, inserting the next floppy and so on. So I had this idea...
What if I stacked 5 floppy drives together, placed all 5 diskettes in them and basically placed an AVR in between the PC and the floppies. I would also need a clock/calender (DS1307) and PC keyboard interface, both of which I have working code for.
I have done some research this afternoon regarding floppy drive interfacing. I noticed that some floppy ribbon cables do the swapping thing with the Drive SelectA, Drive SelectB, Motor EnableA and Motor EnableB signals. I also noticed there are quite a few more floppy interface signals such as Index, direction, read, write, etc.
My question is this: What exactly do the Drive SelectA/B signals do? Do they disable the other signals so that there is no contention between signals if (back in the old days) you really did have 2 disk drives installed? I don't want to switch 'all' those signals such that only 1 drive is physically connected at a time. I was wondering if I could have 5 port lines on an AVR controlling the Drive SelectA line for each individual floppy (obviously there would be another port pin used to read the Drive SelectA line from the PC floppy interface, the AVR would use that and other criteria to select the correct drive).
I realize there will be other 'issues' to deal with such as knowing when a floppy has finished loading but the thought of switching something like 10 signals to each of 5 floppy drives was a project killer to me. Apparently, according to some information I found, the NEC 765 controller was/is capable of sinking (or was it sourcing) around 40 or 50mA on some of those signals.
Anyway, I would be interested in knowing exactly what those Drive Select lines do as I could not find more detailed information.
P.S. If the moderator feels this belongs in the Off Topic forum please move it there, thanks!