Re: Write Signal on Disk II Question

[glen herrmannsfeldt <gah@ugcs.caltech.edu>]

ferdimh@gmx.de wrote:

(snip)

> At the moment I'm thinking of a real analog PLL to recover the
> original clock and use it to clock a shift register.
> BTW, a system that just syncs to the data stream is NOT a PLL. A PLL
> would be able to adjust the clock (i.e. when reading a disk which was
> written on a 320rpm drive on a 280 rpm drive it would sample at
> 220kHz). The Disk ][ controller doesn't do that (no floppy disk
> controller does!), and it's not really needed. A real PLL just
> provides more margin which might be useful in tricky situations (like
> copying copy-protected disks).

It used to be that analog PLLs were common in floppy disk
controllers.  I do remember the discussion about how much
better they were than digital PLLs at the time (around 1982).

-- glen