floppy imaging

Tony Duell ard at p850ug1.demon.co.uk
Thu Dec 22 14:41:05 CST 2005

> On Wed, 21 Dec 2005, Al Kossow wrote:
> > The problem comes with discovering the format. I've read and re-read the
> > 8272 and 765 data sheets. From what I can see the only way to see what
> > sectors are on the current track is to use the ReadID command. This
> > returns the ID bytes from the next sector header to pass under the head.
> > There is no way to automatically dump all the IDs from all the sectors
> > from index pulse to the next index pulse (if there is, can somebody
> > please enlighten me).
> You can read multiple IDs during a revolution (200msec)
> If you don't get 'em all, put in a different delay.

And what happens if you get a task-switch midway through this? 

> A flux transition board (CopyII option board),
> or a machine with a 179x can do a track read, that can be analyzed at a
> glance.
> Got Trakcess in your TRS80 M3/4 software?

Oh, on a WD controller it's a lot easier. I have several disk zapping 
programs for the M3/M4 that do this, and I am pretty sure I have the 
source to at least one of them (from Tim Mann's site). 

I grew up with the WD controllers, and found the 8272/765 a real 
disapointment after those :-)

> You can analyze MOST formats by trying to read a 256 byte, a 512 byte, and
> a 1024 byte sector, such as #2, and then trying the numbers up and down to
> find first and last.  Won't work for sectors whose numbering don't start
> with 0 or 1, or ones with invalid headers (such as side B of Kaypro)

IIRC the sector number is a single byte, so presumably you could try 
reading each sector in turn (0..255) in each size to see what gave no 
errors. I'd thought of doing it that way, but it's going to be terribly 


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