6.2
WAITE
GATE
WRITE OPERATION: PC BOARD 20243-XXX.
FIGURE
21:
Write
Operation
PC Board
20243-XXX
REDUCED
CURRENT
HEAD
SELECT
PULSE
GENERATOR
&.2.1 WRITE GATE
A write sequence is initiated when
~rite
Gate is activated
and
applies +
12
Volts
to
the
center
tap
of
the
selected head.
At
the
same time,
data
is sent
to
the
line
receiver 7L.
&.2.2
LINE RECEIVER
DifferentiaI Write
Data
(precompensated MFM) is received from the controller
and
changed
to
single line.
It
is
then
fed into
the
pulse generator (7K) which
changes square wave
data
to
pulse data. Depending
on
whether plus
or
minus
data
is
to
be written, either pin 7
or
pin
9
of
7H
is activated.
The
amount
of
current
to
be written
is
primarily established by R53. When writing
to
the
inner
heads, 2
and
3, Write current is reduced by adding R52
in
parallel which reduces
the
problems
of
pulse crowding.
24
ST212 PRODUCT MANUAL/Rev. B
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