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M Z 3500
Example 2:
CE330S (light passing through the notch
is sensed and decoded äs write-protect)
(Double side, Double density)
Write enabled
Write protected
Front side
rj;
LV; •* — Light is mterrupted by the label
;
O
0
Front side
C
o
0
- — nhibit notch
Two types of write protection are used and attention
must bepaid to the presience of the label because it may
cause a wrong result if the label is used improperly.
5) Media recording methods
Two recording methode are used:
or double frequency (DF). Clock and data are Written
•
FM method (Single density)
on the media which requires that a clock bit that
This method is called the freqency modulation (FM)
precede the data.
1
0
0
1
0
n n n
n
n n n
n
C
D
C
D
C
D
C
D
C
D
C
(C: clock, D: data)
Waveforms of data Written or read in the FM mode are shown below.
l
4 / ^ S
Write data
(WO)
Write current
Residual magnetic
flux on the media
Read waveform
Differentiale
waveform
Shaped waveform
Read data (RD)
r^
C
D
C
D
C
U
C
D
C
D
C
D
n n n
n
n n n
n
_j
*
/
%
'
\
\
1
1
1
**
/
J
£\
n n
v^H
& uS
0
0
^
^
X ^7-^
/
\
X
T
1
n
h
^
•\
\
vy
l i
n
1
i
*
L
J
r\
n
0
'
•\^
,
h
0
•^
v
^
n
/
> Wrote
V
Read
-
Write current: The write data is input to the flipflop and
is inverted each time a pulse is received to change the
direction of writing current.
at a change of magnetic flux. The waveform is than
shaped to obtain read data identicnl to the write data.
Data cycle will be 4/js.
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