In
dual platter models a low condition on this line selects the top storage surface
of
the
selected platter. When high, the line selects the bottom storage surface of the selected
platter.
In
single platter models, a low condition
on
this line selects
head
0
and
the top storage
surface
of
the platter; when high, head 1 and the bottom storage surface
are
selected,
as
shown in Table3-1.
3.16.4 CYLINDER
ADDRESS
STROBE
This is a pulse which, when low for a minimum
of
0.5fJ.sec and the disk unit is selected
and
ready, causes the
RESTORE
INITIAL CYLINDER line (Paragraph 3.16.6) and
CYLINDER DEMAND
ADDRESS
lines (Paragraph 3.16.5) to be sampled. This will initiate a
Restore operation
or
a Cylinder Seek operation, depending on the state of the
RESTORE
INITIAL CYLINDER line.
For a Restore operation, the CYLINDER DEMAND
ADDRESS
lines
are
ignored
and
the
positioner
will initialize at cylinder 000 (decimal).
For a
Seek
operation,
if
a legal address is presented
on
the CYLINDER DEMAND
ADDRESS
lines, the positioner will seek the cylinder address specified
by
the states on
these lines.
If
an
Illegal address is presented, then the positioner will not move
and
the
illegal condition
will
be
reported on the ILLEGAL CYLINDER
ADDRESS
line.
The desired operation is initiated on the trailing edge
(lOW
to high transition)
of
the pulse.
The
RESTORE
INITIAL CYLINDER line must be
in
a stable state at least 0.5
tJ.sec
prior to
the leading edge (high to low transition)
of
the strobe pulse.
The
CYLINDER DEMAND
ADDRESS
lines must
be
in a stable state at least 0.5
fJ.sec
prior
to the trailing edge
of
the strobe pulse. They must remain in that state during the trailing
edge and for
at
least
0.5!J.sec
after the trailing edge
of
the strobe.
The
BUSY
SEEKING line (Paragraph 3.17.2) will go to a low level within 1.0
f.1sec
after the
leading edge of the strobe pulse.
Table
3-1
Platter and
Head
Selection
PLATTER
HEAD
Dual Platter Models
Single Platter Models
SELECT
SELECT
Line
Line
Storage
Storage
Logic
Logic
Platter
Surface
Head
No.
Platter
Surface
Head No.
Level
Level
Low
Low
Top
Top
0
Top
Too 0
Low
High
Top
Bottom
1
Top
Bottom
t
High
low
Bottom
Top
2
None
None
High
High
Bottom
Bottom
3
None
None
3-14
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