10 Sector Hard sectored disks.

[Chuck Guzis]

On 29 Oct 2007 at 14:42, Atsushi Takahashi wrote:

> When reading, you could sense where the data starts and ends but to
> write to a new disk you'd have to make sure the motor speed was
> constant before trying to generate fake sector hole signals.  Maybe
> some kind of PLL circuit.  Any idea what jitter is allowed? 

It would depend on the format, but there's always a run-in (sync) gap 
on these things.

Here's what I've been thinking.

Time two or three revolutions of a disk after motor on and select 
before generating the index pulse.  If it's a soft-sector disk, 
you'll see a real index pulse every 200 msec. or so and you can 
subdivide the rotation accordingly and update your rotational rate 
metric every revolution. If you see many index pulses, just pass them 
through as you're handling a hard-sector diskette.  You'd need to 
look at drive select, index and perhaps ready as inputs and ready and 
index as outputs.

At first blush, it appears as if a PIC 12F629 8-pin DIP might just be 
able to do the job.

Cheers,
Chuck