30 Nov
2011
30 Nov
'11
12:27 p.m.
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, but only 2 voltage levels.
The circuitry tconvert the signal from the read head toa digital signal
is in the drive (the read amplifier, comparator, monostable, etc). What
uou get at the interface conenctor is a stram of pulses, the leading
edges of which correspond to magnetic transitions on the disk. The
controller has to covert those pulses into parallel words, recognise
sector markers, and the like.
When writign, it's muchte same dviision. The controller takes words from
the host system and serialises them. It also controls when to start/stop
writing on the disk. The interface, again, is a digital pulse stream, the
conversion from that to the head drive signals is done in the drive.
-tony