Seagate ST12450W, Руководство по эксплуатации продукта

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18 ST12450W/WD Product Manual, Rev. A
The host can reconfigure the drive any time after power-up to be the master
or a slave by using the Mode Select command on the Rigid Disc Drive
Geometry page. The master provides the reference signal to which all other
drives phase-lock, including the master. There is only one master per
system, and that can be a drive or the host computer. All drives may be
configured as slaves allowing the host to provide the reference signal.
Each drive also can be configured for the non-synchronized mode in which
it ignores any reference signal that might be present—this is the default
mode as shipped from the factory. Connect the synchronized reference
signal to the host only if the host provides the reference signal. If the host
does not provide the reference signal, do not connect the host.
Rotational position locking
Note. Mode Select page 4, byte 17, bits 1 and 0.
RPL Description
00b Spindle synchronization is disabled (default value)
01b The target operates as a synchronized-spindle slave
10b The target operates as a synchronized-spindle master
11b The target operates as a synchronized-spindle master control
(not supported by the disc drive)
The VIC 2 LSI on the master drive provides the reference signal (SSREF
+
).
The index signal generates a 120 Hz signal. The signal is normally
false/negated (nominal 0V) and makes a transition to the true/asserted
(nominal
+
5V) level to indicate the reference position during the revolution
period. Master and slave drives use the trailing (falling) edge of the
reference signal to phase lock their spindles. A maximum of 10 seconds is
allowed for a slave to synchronize with the reference signal. Figure 5 shows
the characteristics of the reference signal.
T = 0.0083 seconds (
±
1.0% max)
±
10 microseconds cycle-to-cycle variance
±
20 microseconds phase error while synchronized
T
1.0 µsec min.
1.37 µsec max.
0
1
SSREF +
Figure 5. Synchronized reference signal characteristics