Sharp FDD-412A Service Manual page 22

FDD412A/B
(2)
(3)
(4)
(5)
Track OO sensor
The track 00 sensor checks if the magnetic head is positioned on
the outermost track of the medium. The sensing is done by the
carriage's tab coming in between the LED and the sensor for
emission interruption. This operation is used to generate the
reference signal for the FDC.
Fig. 2.8 Track 00 Sensor
Carriage
File protect sensor
The file protect sensor senses the presence or absence of the
inhibit notch on the medium. Upon sensing, the sensor tells the
FDC whether or not writing is available, simultaneously controll-
ing if the FDD write circuit should be operable.
When writing is to be done, use a medium with no inhibit notch or
put a write permission label on the medium.
Inhibit notch
Fig. 2.9 File Protect Sensor
Index-1/2 sensor
The index-1/2 sensor senses the index hole on the medium.
It informs the FDC of the track start point', automatically recog-
nizes the medium type (single-sided or two-sided), and checks the
medium for rotation status.
Index hole 1 (for single-sided disk)
Index hole 2 (for two-sided disk)
Fig. 2.10 Index Hole
Door switch
The door switch checks if the FDD door is closed.
If the door is found open, the FDD is kept from entering the ready
state because the medium is not rotating.
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