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MZ 3500
In the case of the MFM method, need to trace cycle fluc-
tuation is further increased, äs a peak shift is apt to occur
because there are three write data cycles.
(Peak shift): Data read cycles fluctuate äs the flux change
point is moved forwards or backwards.
Write pulse
Polarity Inversion
Advanced peak shift
•— Delayed peak shift
l
Regenerated pulse
\\
jjl
( b )
(VFO Circuit): Variable frequency oscillator
Polarity Inversion
f~J
Write Pu^e
f]
f]
H
R
H
Polarity Inversion
Write pulse
I
Read waveform
6.0 4.0 2.0
0
2.0 4.0 6.0 ( / - s )
( a )
Advanced peak shift —j l—
—| f— Delayed peak shift
( c )
When the Output vaveform is observed after writing a single
pluse on the floppy disk, the waveform show in (a) appears.
Shown in (b) is two pluses of 4^is interval.
Deviation in the peak point iscalled peak shift. Since pluse
intervals of the MFD in actual Operation are 4/is, BAIS, and
8fis, the largest shift takes place when a pluse appears 8/Js
before or after 4/is, äs shown in (c).
5-10. VFO Circuit
1) Purpose
String of data
pulses from the FDD.
Data window
String of
separate data
n
r L
_ n
Data from the clock or data portion must be differentiated
when read from the FDD. For this purpose a window pulse
is used. In order to increase read tolerance, the VFO Circuit
carses the window to trace phase changes in the read data
that take place during a floppy disk drive motor speed
change.
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