13 Jul
2004
13 Jul
'04
7:14 p.m.
Hmm. So in your mind experiment you keep the 12 sector pulses and
the track pulse, and deliver the track pulse with 16 sector pulses
to the hardware of the drive logic.
Using the 12 sector pulses will probably produce a more stable 16
sector pulse signal as the PLL is kept in lock in shorter intervals.
But what would the PLL circuit do when it gets 12 sector pulses
(that is fine) *_and_* at some odd moment the extra track pulse ...?
I was thinking of *only* the track pulse and get the PLL locked on
that pulse only, assuming that the stability of the PLL is sufficient
for one revolution. From the N divider is would be easy to get the
sector pulses. So, I cover all the sector slits on the hub of the disk.
But as you said (I did not know that part and did not check on an RK05
pack I have at home), the track pulse is not halfway two sectors.
Some separate binary comparator could check the N divider outputs and
then you simply set a binary number to the comparator when it should
give the track pulse.
- Henk.
-----Original Message-----
From: cctalk-bounces(a)classiccmp.org
[mailto:cctalk-bounces@classiccmp.org]On Behalf Of Paul Koning
Sent: dinsdag 13 juli 2004 16:38
To: cctalk(a)classiccmp.org
Subject: RE: FW: RK05 question
>>>> "Gooijen" == Gooijen H
<Gooijen> writes:
Gooijen> Isn't the track index pulse == the one pulse that is fed to
Gooijen> the PLL phase comparator? That pulse is used to synchronize
Gooijen> the oscillator that must run at 12 (or 16) times the
Gooijen> frequency between 2 sector pulses to generate the (missing)
Gooijen> sector pulses .... or am I mistaken here?
No, what I meant is to derive the 16x sector pulses from the 12x
sector pulses, keeping the track pulse as it is. But either would be
possible.
The track slot is close to the first sector slot (it's not halfway
between sectors). What I don't remember is how close, or whether the
sector slot spacing around the track index is the same as elsewhere,
or different. That would affect the PLL design a lot...
To do this right would require measuring the angular positions of all
the slots on a 12 sector and 16 sector pack, to see just what the
pattern looks like and how to transform one to the other.
paul