F
FyberOptic
Hiya folks! Due to my constant need to do somewhat useless things just
to see if I can, I decided I want to better learn the workings of a
floppy drive by making a parallel port interface for one. I might also
implement something like this in a homebuilt computer design I've
played around with.
First of all, there's a couple things I'm unsure about on the
connector, so to the pinout!
http://pinouts.ru/Storage/InternalDisk_pinout.shtml (Modern floppies
would use the top pinout table, correct?)
I think there's an error in the signal direction for DSKCHG. I would
assume you read this pin, yet they have it indicated that you write to
it, which makes no sense. The other thing I'm curious about is what
the INDEX signal is for. I guess this might have been used for 5.25"
disks which had that little hole in'em, and I don't even entirely
understand what it'd use that for, but this seems to be a useless
signal for 3.5" if this is the case, since they seem to be lacking such
a hole as far as I can tell.
Now for the meat of the matter. I thought I had the general idea of
how the drive worked down, up until I started writing this post, then I
realized I don't understand a lot more than I realized. I intially
thought it went something like: enable drive select for the drive in
question, enable the motor, set direction, step to track you want.. but
then I realized, how does one actually READ the disk? I mean, I can
step to the track I want, but how do I read off the bits of that track?
I don't see any signals on the connector which could indicate anything
I need to clock. The Drive Select, perhaps, but don't you have to hold
this low for doing any seeking? Or do the bits come out automatically,
in a constant stream, looping over and over? I'd assume that if it did
spit bits out constantly, that this is where the index signal would
come in handy, but again, I'm not even sure 3.5" disks can do that.
I also can't seem to find any definitive reference for the actual
signals needed for each pin, such as what signal to use for density
select to force high-density disks, or what signal means which
direction, etc. I found a reference at one point, but it wasn't
complete, and considering the signals are active-low apparently, I had
no idea if that person took that into consideration or what.
What I thought would be something relatively simple has ended up a bit
trickier than I thought, unless I'm just overlooking something simple.
A good reference would probably help wonders, but it seems I only
manage to find a lot of useless pinouts.
Anyone with any insight on working with floppy drives would be
appreciated!
to see if I can, I decided I want to better learn the workings of a
floppy drive by making a parallel port interface for one. I might also
implement something like this in a homebuilt computer design I've
played around with.
First of all, there's a couple things I'm unsure about on the
connector, so to the pinout!
http://pinouts.ru/Storage/InternalDisk_pinout.shtml (Modern floppies
would use the top pinout table, correct?)
I think there's an error in the signal direction for DSKCHG. I would
assume you read this pin, yet they have it indicated that you write to
it, which makes no sense. The other thing I'm curious about is what
the INDEX signal is for. I guess this might have been used for 5.25"
disks which had that little hole in'em, and I don't even entirely
understand what it'd use that for, but this seems to be a useless
signal for 3.5" if this is the case, since they seem to be lacking such
a hole as far as I can tell.
Now for the meat of the matter. I thought I had the general idea of
how the drive worked down, up until I started writing this post, then I
realized I don't understand a lot more than I realized. I intially
thought it went something like: enable drive select for the drive in
question, enable the motor, set direction, step to track you want.. but
then I realized, how does one actually READ the disk? I mean, I can
step to the track I want, but how do I read off the bits of that track?
I don't see any signals on the connector which could indicate anything
I need to clock. The Drive Select, perhaps, but don't you have to hold
this low for doing any seeking? Or do the bits come out automatically,
in a constant stream, looping over and over? I'd assume that if it did
spit bits out constantly, that this is where the index signal would
come in handy, but again, I'm not even sure 3.5" disks can do that.
I also can't seem to find any definitive reference for the actual
signals needed for each pin, such as what signal to use for density
select to force high-density disks, or what signal means which
direction, etc. I found a reference at one point, but it wasn't
complete, and considering the signals are active-low apparently, I had
no idea if that person took that into consideration or what.
What I thought would be something relatively simple has ended up a bit
trickier than I thought, unless I'm just overlooking something simple.
A good reference would probably help wonders, but it seems I only
manage to find a lot of useless pinouts.
Anyone with any insight on working with floppy drives would be
appreciated!