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1.15.3
Spindle Drive 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.
READY
CONTROL
INDEX
LOGIC
DISK CHANGE
TWO SIDED
WRITE PROTECT
TRACK 00
IN USE
SIDE SELECT
HEAD CARRIAGE
DRIVE SELECT
AND STEPPER
BAND
ASSEMBLY
SPINDLE
MOTOR CONTROL
MOTOR
CONTROL
WRITE GATE
WRITE
WRITE DATA
LOGIC
CURRENT SWITCH
READ
READ DATA
LOGIC
DIRECTION
STEPPER
MOTOR
CONTROL
STEP
Figure 1-2
TM848 Disk Drive Functional Block Diagram
1.15.4
Positioner 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 Electronics
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.
1-9
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