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Tandy 1000 Technical Reference Manual

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Tandy 1000
Technical Reference Manual
Outputs
of
the
direction
latch
and
the
internal
step
pulse
generator
are
input
to
the
shift
register
and
phase
drive
selector,
and
they
are
converted
to
the
appropriate
timing
signals
for
uni-polar
1-2
phase
drive
of
the
4-phase
stepping
motor.
These
phase
drive
signals
are
supplied
to
the
stepping
motor
driver,
US
(output
pins
12
~
15).
In
order
to
improve
the
torque
margin
in
the
seek
operation,
partially
2-phase
drive
period
is
provided
by
the
phase
drive
selector
only
in
the
initial
stage
when
the
drive
phase
is
changed.
When
the
head
stops
on
an
even
track,
phase
A
is
magnetized,
while
phase
A
is
magnetized
when
the
head
stops
on
an
odd
track.
The
phase
Band
B
are
magnetized
only
during
the
seek
operation.
The
output
from
the
internal
step
pulse
generator
is
also
supplied
to
the
over-drive
timer
constructed
with
a
re-triggerable
counter.
During
the
active
period
of
this
timer
(7Smsec,
approx.),
+12V
power
is
supplied
to
the
stepping
motor
coils
through
the
over-drive
circuit
(Ql)
to
produce
enough
torque
required
for
the
head
seek
and
the
settling
operations.
After
the
completion
of
the
settling,
only
+SV
power
is
supplied
to
the
stepping
motor
through
the
diode,
CRl,
which
minimize
the
power
loss
by
supplying
only
the
required
torque
for
the
holding
of
the
stop
position.
By
the
above
consideration,
heat
radiation
from
the
motor
is
depressed
to
the
minimum
level
and
the
stepping
motor
power
consumption
of
O.33W,
approx.
at
the
stop
condition
is
achieved.
-
318
-

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Tandy 1000 Specifications

General IconGeneral
ProcessorIntel 8088
Processor Speed4.77 MHz
RAM128 KB (expandable to 640 KB)
Operating SystemMS-DOS 2.11
ManufacturerTandy Corporation
Release Year1984
StorageSingle or double 5.25" floppy disk drive (360 KB), optional hard drive
SoundTandy 3-voice sound
PortsParallel, Serial
GraphicsCGA (Color Graphics Adapter)
Graphics Modes320x200, 640x200

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