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1.15.3
Sp in d l e D rive System
The spindle drive system consists of a spindle assembly driven through a drive belt by a brushless
D.C. motor/tachometer.
The servo electronics required for speed control are located on the printed circuit board.
The control circuitry contains an interface control line. When the drive motor control interface line is
false (high), the drive motor is allowed to come up to speed.
D.C.
STEPPER
MOTOR
HEAD CARRIAGE
AND STEPPER
BAND
ASSEMBLY
1.15 4
Po s i t i o ner Control
The head positioning system uses a bipolar-driven motor drive, which changes one phase for each
track advancement of the read/write carriage. In addition to the logic necessary for motor control, a
gate is provided that inhibits positioner motion during a write operation.
1.15.5
Data E l e c t r onics
Information can be recorded on the diskette by using a double-frequency code. Figure 1-3 illustrates
the magnetization profiles in each bit cell for the number sequence shown for FM recording.
INDEX SENSOR
L.E.D.'S ~
WRITE PROTECT
+
SENSOR
L.E.D.
INDEX DETECTORS
WR ITE
PROTECT
DETECTOR
Figure 1-2
TM848 Disk Drive Functional Block Diagram
1-9
CONTROL
LOGIC
SPINDLE
MOTOR
CONTROL
D.C. DRIVE
WRITE
MOTOR
LOGIC
READ
LOGIC
STEPPER
MOTOR
CONTROL
READY
INDEX
DISK CHANGE
TWO SIDED
WRITE PROTECT
TRACK 00
IN USE
SIDE SELECT
DRIVE SELECT
MOTOR CONTROL
WRITE GATE
WRITE DATA
CURRENT SWITCH
READ DATA
DIRECTION
STEP
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