Tandy 1000 Technical Reference Manual

Tandy 1000
Technical Reference Manual
-I
Off-delay
signal .~L. ....J
on_d.'~
WRITE GATE input
TP2(Erase gate)
(Fig.313) Typical waveform of TP2(for tunnel erase head)
Delay
Straddle erase head Tunnel erase head
On-delay
OV
s
200 '\,
320vs
Off-delay
OV
s
860 '\,
950vs
(Table 302) Erase gate delay
(3) TP3 (Phase B)
Test point to observe the phase B magnetized period of the stepping
motor.
The stepping motor rotates for 2-steps in response to one STEP input
pulse. Therefore, TP3 becomes HIGH level for a specified period when
a step-out command from an even track or when a step-in command from
an odd track is executed. Refer to Fig.310.
(4) TP4 (Index)
Test point to observe the output of the index detection photo-transistor
(shumitt inverter included) .
The signal level at this TP is opposite to that of INDEX output signal.
When the index hole or sector hole (hard sectored disk) is detected,
HIGH going pulse is observed at TP4. The photo-transistor is mounted
on the front OPT ASs'y and the LED is mounted on the back side of the
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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