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Example 2:
CE330S (light passing through the notch
is sensed and decoded as write protect)
(Double side, Double density)
Write enabled
Front side
O
0
Light is interrupted by the label
Write protected
Front side
o
0
-r- 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:
•
FM method (Single density)
This method is called the freqency modulation ( F M )
1
0
0
n n n
n
C
D
C
D
C
D
C
or double frequency (DF). Clock and data are written
on the media which requires that a clock bit that
precede the data.
I
fL_JL_fl
0
JL
(C: clock, D: data)
Waveforms of data written or read in the FM mode are shown below.
r*-
Write data
(WD)
Write current
Residual magnetic
flux on the media
y
Differentiate
^
waveform
Shaped waveform
Read data (RD)
T_J
—
•«—
\
_
fi_i .— >
9 US
4
D
ILJ
1
L_J
— *•
/
J
r\
i — i
i_
k
C
I)
C
D
C
n
n
n
0
^v
n
0
»•
^s
r/
n
l — i
. « —
~\
\
vy
i i
fl_J
D
ILJ
1
1
— »•
J
r\
rn
n_j
C
D
C
D
i
n i
0
+
"^
X
n
0
•\
y
f-'
L
J
>
Wrote
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.
Read waveform: The peak of the waveform is detected
at a change of magnetic flux. The waveform is than
shaped to obtain read data identic it >. < _• tlirf write data.
Data cycle will be 4/^s.
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