Seagate Hawk 2 ST11900N, Product Manual

Page: 24 / 82

16 Product Manual - Hawk 2 Family SCSI-2 (Volume 1), Rev. C
_________________________________________________________________________________________
The servo/read-write LSI on the master drive provides the reference signal (). It is a 90.18 Hz crystal
generated signal. The signal is normally false/negated (nominal 0 V) and makes a transition to the true/asserted
(n5 V) level to indicate the reference position during the revolution period. The trailing (falling) edge of the
reference signal is used by the master and the slave drives to phase lock their spindles. A maximum of 10
seconds is allowed for a slave to synchronize with the reference signal. Figure 5.7-2 shows the characteristics of
the reference signal. The signal (available on J7-6. See Figure 5.7-1) of each synchronized drive shall
occur 85.2 µsec +20 µsec after the signal. Figure 5.7-2 shows the characteristics of the reference
signal.
T
0.5 usec min.
500 usec max.
0
1
T = 0.0111 second (+/- 1.0% max); +/- 10 usec cycle to cycle variance.
Figure 5.7-2. Synchronized reference signal characteristics