Specifications
In
the
standard
configuration, the host system turns off
the
motor by deactivating
the
DRIVE SELECT line. This
should be
done
if
the drive has not received a
new
command
within
2.6
seconds (16 revolutions of diskette) after
completing
the
execution of a
command.
This
will
ensure maximum
motor
and
media life. Also, the
2.6
second
delay function
can
be
done
by the drive by jumpering
the
optional Motor Off delay. Refer to
paragraph
7.10.
1.4.4
Track
Accessing
Seeking the
read/write
heads
from
one
track to
another
is
accomplished by:
a. Activating DRIVE
SELECT line.
b. Selecting desired direction utilizing DIRECTION
SELECT line.
c. WRITE GATE being inactive.
d.
Pulsing
the
STEP line.
Multiple track accessing
is
accomplished by
repeated
pulsing of the
STEP
line until the desired
number
of steps
have
been
input. Each pulse on the
STEP
line
will
cause the
read/write
heads
to
move
one
track either
in
or
out
depending
on
the DIRECTION SELECT line.
Head
movement
is
initiated
on
the
leading
edge
of the
STEP
pulse.
Pulses received at less
than
a 3 ms period, but greater
than
15
p,S,
will
be stored in a buffer which
will
then
issue step
commands
to the drive stepper motor at a 3 ms pulse rate. Pulses received at greater
than
a 3 ms period
will
step
the
drive at
the
same
rate they are received.
The
first step begins
upon
receipt of
the
first
step pulse.
1.4.5
Step
Out
With the DIRECTION SELECT line at a plus logic level (2.5 V to
5.25
V), a pulse on
the
STEP line
will
cause
the
read/write
head(s) to
move
one
track away from the center of the disk. The pulse(s) applied to the
STEP
line must
have
the
timing characteristics shown
in
figure 1-3
or
figure 1-4.
1.4.6
Step
In
With
the
DIRECTION SELECT line at a minus logic level
(0
V to
0.4
V), a pulse on
the
STEP line
will
cause
the
read/write
heads
to
move
one
track closer to
the
center of the disk. The pulse(s) applied to the STEP line must
have the timing characteristics shown
in
figure 1-3 or figure 1-4.
DC POWER
-I--------------~u~-------------
DRIVE SELECT
I
I
--------------~i~2------------------
DIRECTION SELECT
________
OUT
~
I IN
i~
STEP
-I1--11'S
~
1-
1
1'5
MIN
~~S
_I
1-16
ms MIN
-I
r-
1
1'5
MIN
---------~
~--
11'5
MI~
~
~
3 ms MIN"
-1
1---3
ms MIN"
*3
ms
is
the
minimum
frequency for a standard seek. Pulses received at less than a 3
ms
frequency
will
go
into
a buffered seek mode. See figure
1-4.
39216·03·A
FIGURE 1·3. TRACK ACCESS TIMING, STANDARD SEEK
1-6