BASF 6106 - Stepper Motor Control; Write Gate

2.2.2.
STEPPER
MOTOR
CONTROL
The
stepper
notor
is a
four phase
DC
-
Botor
and
is
controlled
by
the
integrated
circuit
SAA
1027.
This
IC
comprises
the stepper
Mo-
tor
drivers,
a
synchron
counter
and
control
circuits
(see
Fig.
2
-
16).
Each
STEP
pulse
froa
the
host
systen
rotates
the
stepper
mo-
tor
for
one
step.
Each
step
corresponds
to
a
rotating
angle
of
15°.
The
rotation
of
the
stepper
Botor
is
converted
to
a
linear
Motion
of
the R/W-
head by
the
spiral
wheel.
The
direction
of
the
aotion
of
the R/W-
head
de-
pends
on the
input
signal
DIRECTION
IN/.
If
this
signal
is active
(low)
the
R/W-
head
will
be
»oved
towards
track
39
(in).
The
R/W-hcad
oves
out by
each
STEP-pulse,
when
DIRECTION
IN
/
is
in
a high
state.
Multiple
track
positioning
is
attained
by
the
host
system
issuing
a se-
ries
of STEP
pulses
at
12
Msec
intervals.
Table
2-4
shows
the
output
signals
for"in
M
and
"out"
notion
of
the
R/W-
head.
The
DIRECTION
IN
signal
aust
be
at
the
desired
level
1
/usee
before
the
trailing
edge of
the
STEP
pulse.
Stepping
is
initiated
by the
trailing
edge
of
the
step
pulse.
The
time
between
two
consecutive
STEP
pulses
must
be
12 asec
Binimum
(see
Fig.
2-17). As
long
as
WRITE
GATE
/
or
WRITE
INHIBIT
is
active
during
a
write
operation
the
STEP
pulse
in-
terface
line
is
inhibited
in the
input
inter-
face
logic.
I N
STEP
PHASE
A/ B/
C/ D/
L
H
L
H
H
H
H
L H
L
L H H
L
L H
L H
STEP
OUT
PHASE
A/
B/ C/
D/
H
H
L H
H
L
H
L H
L
H
L
L H
L H
L H
TABLE
2
-
4
. SEQUENCE
OF
THE
STEPPER
MOTOR
SIGNALS