amiga floppy disk reading experience

[Eric Smith]

On 06/12/2010 11:21 PM, Chuck Guzis wrote:
> It should be observed that the typical "time since last pulse" sort
> of data collection done by most of these things (e.g. Catweasel) and
> inerpreted by a "threshold" sort of algorithm does constittute a PLL
> of sorts, since phase errors tend to self-correct long-term speed
> variations (i.e. every sample is relative only to the previous one).
>
> In other words, if the drive is spinning too slowly and pulses (1t,
> 1.5t and 2t for MFM) come a bit late, the error isn't cumulative.
>    
It's not a PLL since it doesn't even try to adjust the frequency to 
maintain phase lock.  It only changes the instantaneous phase.  There's 
no "Loop" in it, nor "Lock".

Eric