Tandon TM848-1, Руководство по эксплуатации и обслуживанию

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Figure 3-9
Track 00 Schematic Diagram
Circuit Description
When the read/write carriage is restored to Track 00, a tab on the carriage blocks light from the Track
00 L. E. D., turning off the Track 00 sensor transistor. This enables the inverting input of U32, a quad
comparator causing U32, Pin 13, to go high.
This signal is gated with Phase 0 of the step circuit and with drive select to generate the signal TRK
00. The signal at Test Point 10 should go high between Tracks 2 and 3, as the carriage is being moved
toward TRK 00.
E. WRITE PROTECT
Functional Description
When the drive is selected and the diskette is write protected, the WRITE PROTECT line's true (low).
The write electronics are internally disabled when the diskette is write protected (see Option Listing
for exceptions).
When the signal on the WRITE PROTECT line is false (high), the write electronics are enabled and the
write operation can be performed. It is recommended that the controller not issue a Write command
when the Write Protect signal is true (low).
It is recommended that the Write Data line be inactive whenever Write Gate is false (high).
Circuit Description
When a write protected diskette is installed, light from the Write Protect L. E. D. is detected by the
Write Protected sensor transistor. The output of the sensor is high and is conditioned by U32. The
output at Pin 14 is lo w g e n e r a t ing t h e s i g nal WR PROT-. This signal is used internally with the
read/write circuitry. The signal WR PROT- is inverted by U33, and gated with DR SEL+ to generate
the Write Protect signal.
F. READ DATA
Functional Description
The Read Data interface line transmits the read data to the controller when the drive is selected. It
provides a pulse for each flux transition recorded on the media. The Read Data output line goes true
(low) for a duration of 200 nanoseconds for each flux change recorded.
The leading edge of the low going, read data output pulse represents the true positions of the flux
transitions on the diskette surface.
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