Tandy 1000 Technical Reference Manual

Tandy 1000
Rotation starts
Disk speed
Index sensor output
(TP4)
speed detector
output in U2
Technical Reference Manual
Constant speed
Pre-ready latch
in U2
Ready latch output
(U2, pin 12)
READY signal
600msec Max.
800msec,Max.
Pre-ready
I
state
Ready state
(Fig.309) Ready detector waveforms
Stepping motor control circuit is constructed with direction latch,
internal step pulse generator, shift register, phase drive selector,
overdrive timer, etc.
Direction latch is a circuit to sample and hold the head seek
direction designated by the DIRECTION SELECT signal at every input
of the STEP pulses.
The internal step pulse generator is constructed with a counter and
a pulse generator. The counter is triggered at the trailing edge
of the STEP input pulse, and the second internal step pulse is
generated with a delay of ~msec, approx. from each STEP input pulse by
the pulse generator. It makes the stepping motor rotate for 2 steps
(3.6°) in response to one STEP input pulse.
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Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200