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The
drive
electronics
conditions exists:
iynore
step
pulses
when
one
of
three
1.
~he
write enable is true (low).
2.
The direction select is false (high), and the head is
positioned at Track O.
3.
The drive is not selecterj.
Composite Write Data
When
the
drive
is
selected,
this
interface line provides the bit
serial composite
write
data pulses that control the switching of the
write
current
in
the
selected head.
The write electronics must be
conditioned for writing by the Write Enable line.
For
each
high-to-Iow
transition on the Composite
flux
change
is
produced
at the write head gap.
change to be recorded on the media.
Write Data line, a
'[his causes a flux
When
a
single-density
(FM) type encoding technique is used in which
data
and clock form the combined Write Data signal,
it is recommended
that
the repetition of the high-to-Iow transitions, while writing all
zeros,
be
equal to one-half percent, and the repetition of the high-
to-low
transitions,
when
writing
all ones, be equal to the maximum
data rate, 250 kilohertz
~
0.1 percent.
Host
controllers
may
implement
write precompensation circuits that
recognize
worst
case
patterns
and
adjust the write data waveform.
Al though a value cannot be spec i f ied for wri te precompensat ion, Tandon
suggests
a
value
of
250
nanoseconds
for systems using MFM double
density recording format.
Write Enable
When this signal is true (low), the write electronics are prepared for
writing data and the read electronics are disabled.
This signal turns
on
write
current
in
the selected read/write head.
Data is written
under
the
control
of the Composite Write Data and Side Select input
lines.
When
the
write
Enable
line
is
false
(high), all write
electronics are disabled.
diskette is installed in a drive,
irrespective
of
the
state of
When
a
write
protected
electronics
are
disabled,
Enable or Side Select lines.
Side Select, TM50-2
the wri te
the Write
The
Side
Select
interface
line
defines
which side of a two-sided
diskette is used for information transfer.
3-5
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