Sharp MZ-3500 service manual TJ ILJ n

Example 2:	CE330S (light passing through the notch
	is sensed and decoded as write protect)
	(Double side, Double density)
	Write enabled	Write protected
	Front side	Front side
	Light is interrupted by the label	-r-nhibit notch
	O	o
	0	0

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)

n 1 n n 0

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.

0	I	0
	n fL_JL_fl	JL
D	C

(C: clock, D: data)

Waveforms of data written or read in the FM mode are shown below.

r*-

(WD)		D	C I)	C D	C	D	C	D	C	D
		T_JILJn		n		ILJin			n	i
Write data
		1	0	0	l—		i	0		0
Write current		—L_J				1				1	> Wrote
Residual magnetic		•«— —*•		»•	.«—	— »•		+
flux on the media											•\
	y \		/^v	^s~\			"^		Xy
		J		r/	\J						Read
		r\			vyr\				f-'
Differentiate	^
waveform
Shaped waveform		_—i	i		i	rni			LJ
Read data (RD)		fi_ii_n		n	fl_Jn_jn
		.—>	k
		4
		9 US

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.