1 Dec
2011
1 Dec
'11
12:12 p.m.
On Dec 1, 2011, at 2:53 PM, Brent Hilpert wrote:
On 2011 Nov 30, at 12:27 PM, Tony Duell wrote:
Not really. The pulses or flux transitions from the disk are in discrete time slots
relative to each other, albeit with some fluctuation due to physical reality, but that
fluctuation is not part of the intended information content.
It is not like pulse-position-modulation or pulse-width-modulation where the intended
information is represented by a continuous value ('analog') of the time between
two events (edges).
I'm pretty sure what Tony meant was that it's coming off an analog amplification
chain that gives you flux transition outputs; it's not quantized by any digital
circuitry. Thus it's analog in the time domain and not synchronous to any discrete
clock.
The one thing you *do* need to be careful about is that you oversample enough that the
time domain aliasing doesn't give you wrong results (i.e. if your data rate is 30 MHz
and your sampling clock is 33 MHz, you will have problems).
If the sampling hardware is running at 100MHz, you should be fine.
- Dave
- Dave
MFM
drives are not portable across controller models. And at least
sometimes, they're not even portable across examples of a given model of
controller. Remember that the _analog_ waveform is passed up the cable
to the controller, where the discriminator turns it back into bits.
Actually, it's analogue in the time domain