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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
W£SJ
illL 2500
Write protected
Front side
~
--- LIght IS Interrupted
by
the label
I
~
-
Inhibit notch
o
o
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 (FM)
o
c
D
c
D
c
(C: clock,
D: data)
o
D
c
o
o
or double frequency (DF). Clock and data are written
on the media which requires that a clock bit that
precede the data.
o
D
c
D
c
Waveforms of data written or read in the FM mode are shown below.
Write data
(WO)
Write current
Residual magnetic
flux on the media
Read waveform
14
4pS
·1
c
D
C
J)
C
0
:~9
I
I
I
,
D
C
D
C
D
C
D
0
0
0
Wrote
,
,
Re:.d
Differentiate
waveform
: '/\
~
'r\
~
:
I
:
:
:
:
Shaped waveform
Read data (RD)
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.
J.
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
11 k
~:,"
write data.
Data cycle will be 4/1s.
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