I think the
difference between our approachies is that you're
consisderign a drive and a particular controller combination, I am
considering jus tthe drive.
Well, I wasn't really thinking of the controller, rather the signal
one typically sees, which - if you like - implies a controller, as
something wrote the original signal.
The original context of the thread was recovering digital data from
an ST-506 drive, albeit one with unknown controller characteristics,
"Waveforms" were mentioned. I allowed for the benefit of using an
analog-in-the-time-domain assessment of the signal from the drive in
my first message.
Indeed. The point being that for that data to exist, a controller must
have formatted and written to the drive.
Now I will gladly accept that (just about?) any ST506 controller writes
digital data ot the drive by using pulses with only a few differnet
seaprations. Exaclty what pulse seaprations are valid, thoug, does depend
o nthe controler that wrote the data.
So if you don;t know much about the cotnroller, it's proably best to hink
of this as a time-analogue signal, sample it as such amd then decode it.
If there is a debate still it seems to be one of
semantics. Is a wire
interconnecting a gate output and gate input of two TTL ICs in a
synchronous system analog? Or is it an analog *link*? Or is it just
*capable* - if extracted for another use - of being an analog link?
I would argure a piece of wire could be used as analosgue link, althogh
here it's carrying a digital signal.
Suppose youy have a wire that you know is carrying a digital 2-state
signal. It would be foolish to assume it _must_ be a TTL level signal.
You'd start (or at leat I'd start) by looking at it as an analogue signal
(using a 'scope, say) and then figure out what hte votlage lewves were.
Once that's known, you'd then tread ti as a digital signal.
And I feel the ST506 problem is the same, albeit in the time domain, not
the voltage domain. Start by treating the time as 'analuge', only afte
you realise how the data is encoded do you try to 'digitise' the pulse
spacings.
-tony