1 Dec
2011
1 Dec
'11
12:40 p.m.
Tony Duell wrote (about the read data signals of the ST506/412 drive
interface):
Actually, it's analogue in the time domain
Brent Hilpert wrote:
Not really. The pulses or flux transitions from the
disk are in
discrete time slots relative to each other,
When writing, sure.
albeit with some fluctuation due to physical reality,
but that
fluctuation is not part of the intended information content.
No, but it's part of what you actually get when you read data from the
drive, so therefore the raw read data at the interface is not
time-quantized, which is what Tony said. It is part of the job of the
data separator to time-quantize it back to discrete bit (and clock
windows), and doing a good job of that is extremely non-trivial.
What *is* trivial is to time-quantize it to some window that is
significantly smaller than the bit window (i.e., higher sampling
frequency), which is what the Catweasel and Diskferret do. At that
point it is time-quantized but not fit into bit windows, so data
separation is still required.