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The output signal from the read/write head is amplified by a read preamplifier and filtered by a low-
pass linear phase filter to remove noise (see Figure 1-5). The linear output from the filter is passed to
the differentiator, which generates a wave form whose zero crossovers correspond to the peaks of the
Read signal. This signal is then fed to the zero crossing detector and digitizer.
LINEAR OUTPUT FROM FILTER
OUTPUT FROM DIFFERENTIATOR
READ DATA INTERFACE
T = 0 is defined as 250 milliseconds after drive motor starts, or 20 milliseconds after a step
command, or 100 microseconds after termination of write busy, whichever is the latest time.
The zero crossover detector and digitizer circuitry generate a 200 n a n osecond read data pulse,
corresponding to each peak of the read signal. The composite read data signal is sent to the user
system via the read data interface line.
1.16
I NTER F ACE ELECTRONICS
All interface signals are TTL compatible. L o gic true (low) is +0.4 volt maximum, logic false (high) is
+2.4 volts minimum. The maximum interface cable length is ten feet. It is recommended that the
interface cable be flat ribbon cable that has a characteristic impedence of 100 ohms.
1.16.1
Int e r f ace Connector Pin Assignments, P13
The interface connector pin assignments, P13, are listed in Table 1-3.
1.16.2
Pow e r C o n n ector Pin Assignments
The power connector pin assignments are listed in Table 1-4.
DIFFERENTIAL DROOP
I = o
Figure 1-5
Read Timing Diagram
1-12
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