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5.2.4
DATA TRANSFER
LINES
All
lines
associated
with the transfer
of
data
between
the
drive
and
the
controller
are
differential
in
nature
and
may
not
be
multiplexed.
These
lines
are provided
at
the
radial
data
cables
of
each
drive.
Four
pairs
of
balanced
signals
are
used
for
the
transfer
of
data
and
clock;
NRZ
WRITE
DATA.
NRZ READ
DATA,
WRITE CLCXK,
and
READ/REFERENCE
CLOCK.
5.2.4.1
NRZ WRITE DATA
This
is
a
differential
pair that
defines
the
data
to
be
written
on
the
disk.
This data
is
ctocked by
the
WRITE CLOCK
signal.
5.2.4.2
NRZ
READ DATA
The
data recovered by reading
previously
written
information
is
transmitted
to
the
controller via
the
differential
pair of
NRZ READ DATA
lines.
This
data
is
clocked
by
the
READ CLOCK
signal.
NRZ READ DATA
is
held
at
a zero
level
until
PLO
sync has
been
obtained
and
data
is
valid.
5.2.4.3
READ/REFERENCE
CLOCK
The
READ CLOCK
signal
is
provided
to
clock
NRZ READ DATA
and
is
valid
when
READ
GATE
is
active
and
PLO
Synchronization
has
been
established.
The
REFERENCE CLOCK
signal
shall
determine
the
data
transfer rate
and
is
valid
when
READY
is
asserted
and
READ
GATE
is
inactive.
All
transitions
between
REFERENCE CLOCK
and
READ CLOCK
is
performed
without
glitches.
5.2.4.4
WRITE
CLOCK
WRITE CLOCK
is
provided
by
the
controller
and
is
at
the
bit
data
rate.
This clock frequency
is
dictated
by
the
READ/REFERENCE CLOCK
during the
write
operation.
WRITE
CLOCK
should
be
supplied before
beginning a
write
operation
and
should
last for
the duration
of
the
write operation.
5.3.
COMMANDS
AND RESPONSES
5.3.1
COMMAND
STRUCTURE
28
Section
S:
Drive Interface
Explanation
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