Specifications
2.2.12
Output
Lines
There
are nine standard output lines from the
SA810/860
with two optional output lines
and
two alternate outputs
available. The output signals
are
driven with an
open
collector output stage capable of sinking a maximum of
40
rnA at a logical zero level
or
true state with a maximum voltage of
0.4
V measured
at
the
driver. When the line
driver
is
in
a logical
one
or false state,
the
driver
is
off
and
the collector current
is
a maximum of
250
p.A.
See
figure
2-2 for the
recommended
circuit.
2.2.13
Track
00
The
active state of this signal,
or
a logical zero, indicates when the read/write
heads
of the drive are positioned at
track
00
(the outermost track)
and
the access circuitry
is
driving current through
phase
one
of the stepper motor.
This signal
is
at a logical
one
level, or false state, when the read/write
heads
of the selected drive are not at track
00. .
2.2.14
Index
This interface signal
is
prOVided by the drive
once
each revolution of the diskette (166.67 ms) to indicate the begin-
ning of the track. Normally, this signal
is
a logical
one
and
makes the transition to
the
logical zero level for a period
of
0.2
to
2.4
ms once
each
revolution. The timing for this signal
is
shown
in
figure 2-3.
To
correctly detect INDEX at
the
control unit, INDEX should be false at DRIVE SELECT time; that
is,
the
controller
should see the transition from false to true after the drive has
been
selected. INDEX pulses
will
only be provided
when
the
diskette
is
up to speed.
U 0.2
to
2.4 ms =u=
39216·11
FIGURE 2·3. INDEX TIMING
2.2.15
Sector
(Hard
Sector
Only)
When
a hard sectored diskette
is
inserted
and
up to speed, this interface signal
is
provided by the drive
32
times
each
revolution. Normally, this signal
is
a logical
one
and
makes the transition to a logical zero for a period of
0.4
ms
each
time a sector hole
on
the diskette
is
detected. Figure 2-4 shows the timing of this signal
and
its
relationship
to the INDEX pulse.
I~
~
15.20
:!: 0.30 ms
~
r-
0.4 ± 0.2 ms
SECTOR
U
U
U
SS
U
U
INDEX
I
SS
~
U
~-
2.60 ± 0.15 ms
39216·12
FIGURE 2·4. SECTOR TIMING
2.2.16
Ready
This interface signal indicates that two index holes have been
sensed
after properly inserting
and
clamping a
diskette. Three holes have to be sensed for two sided diskettes. Whenever the
door
knob
is
rotated to the closed
position, the spindle motor
will
be activated by the drive until the READY signal
is
generated.
2-5