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The servo electronics required
for
speed control are associated with the spindle drive motor.
The control circuitry also
includes
a current
limiter
and interface control line. When the Drive Motor Enable inter-
face
line
is
true, the drive motor
is
allowed
to
come up to speed. When the current through the drive motor ex-
ceeds 1.3 ampere,
the
current
limit
circuitry disables the motor
drive.
#'INDEX
..
EMITTER
O.C.
STEPPER
MOTO
INDEX
/ ~ • / Ce1!
PULSE
PULSE SHAPING
~:., r
-c,-"
NETWORK
A
I
BAND DRIVE
AND
he:
HEAD ASSEMBLY
WRITE
~
PROTECT
WRITE
bETECTOA
D.C.
DRIVE
PROTECT
~~
SWITCH
TRACK
~
00
TRACK
e8
SWITCH
. .
DRIVE
MOTOR
ENABLE
SPINDLE DRIVE
-
INTERFACE
CONTROL
CONTROL
•
DIRECTION
POSITION ER
STEP
CONTROL
t
WAITE BUSY
WRITE
WRITE
/
ERASE
DATA
CURRENT
SOURCE
ANO
WAVEFORM
GENERATOR
WAITE ENABLE
SIDE SELECT
READ DATA
READ AMPLIFIER
AND DIGITIZER
Figure 1-2
TM-100 Disk Drive Functional Block Diagram
1.16.5
Positioner Control
The Head Positioning system utilizes a four-phase stepper motor
drive,
which changes one phase for each track
advancement of the Read/Write carriage. In addition to the logic necessary for motion control, a gate
is
provided
which
inhibits
positioner motion during a write operation.
1.16.6
Data Electronics
Information can be recorded on the diskette by using a double-frequency code. Figure 1-3 illustrates the magneti-
zation profiles
in
each bit cell
for
the number sequence shown for FM recording.
The erase gaps provide a guard band on either side of the recorded track. This provides flexibility in track posi-
tioning.
All signals required to control the data electronics are provided by the user system and are shown in the TM-100
disk drive functional block diagram
(see
Figure 1-2). These control signals are:
1.
Select
2.
Write Enable
1-8
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