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Circuit Description
The disk change flip-flop, U10, is reset by OPEN- whenever the lever is in the open position. When this
occurs, U10-6 is high, and a true disk change status is sent to the interface on Pin 12 from U4-11. Flip-
flop U10 is set on the trailing edge of drive select causing U10-6 to go low and setting the disk change
status to the false state.
In actual use, this signal can be used by the host controller to determine that the diskette lever has
been opened since the end of the previous drive select operation.
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Figure 3-7
Index Schematic Diagram
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166.667ms
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Figure 3-8
Waveform at Test Point 11 or 12
Alternate Test Point, R33
Soft Sectored Diskette Installed
D. TRK 00
Functional Description
When the drive is selected, the Track 00 interface signal indicates to the controller that the read/write
head is positioned at Track 00. The Track 00 signal remains true (low) until the head is moved away
from Track 00. The Track 00 sensor is activated internally between Tracks 2 and 3.
Interface Pin 42 (see Figure 3-9) is true (low) when the carriage is positioned at Track 00 and the step
motor is at Phase O.
3-11
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