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3.1.3 Operating Sequences
Initialization
1.
2.
3.
Seek
The drive motor turns continuously while
the system power is up.
Insert the diskette and close the cover to
engage the collet assembly
iii
in the
drive hub
D
and clamp the diskette in
place. With the system power up, the
diskette turns.
Index pulses
m
are read every 166.6 ms
nominal when the diskette is up to speed.
1.
Head location is determined by returning
the head to track 0 or by reading the track
address in the 10 field.
2.
Two adjacent access lines must be energized
simultaneously for a minimum of 50 ms
to seek one track
D .
The timing sequence
example illustrates moving the head from
track 2 to track 6. Before a read or write
operation, the two access lines for the
selected track must be energized for 150 ms
minimum
m
(50 ms for travel and 100 ms
to stabilize).
+
Access 0/1
3.
For each access command, the stepper
motor
II
rotates the leadscrew
Ii
90
degrees clockwise or counterclockwise.
This moves the read head one track posi-
tion. (Clockwise rotation of the leadscrew,
looking down on the unit, moves the
carriage up.)
An explanation of the stepper motor is in
Appendix B-1.
B--+-+-II:
D-·~~~~~/J
H
m
Track 0
+
Access 1/2
A
(white)
=\
From
33FO
Attachment
+
Access 2/3
+
Access 3/0
AC Power
m
+
Head Load
Track 1
(red)
Head Load
Magnet
Driver
3-6
Read or Write
1.
2.
3.
The head load line
m
is activated before
and during any read or write operation.
This causes the pressure pad
m
to push
the flexible diskette against the read/write
head
ri .
After 80 ms, data can be read
or written
II .
Reading or writing occurs.
The pressure pad is lifted as soon as possi-
ble after completion of the last read or
write operation to reduce diskette and
head wear.
Index
Amplifier
m
+
Index Pulse
To 33FD
Attachment
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