Seagate ST15150N Product Manual - Page 28

18 ST15150N/ND/W/WD/WC/DC Product Manual, Rev. D 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. The connection of the synchronized reference signal to the host is required 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 Pike 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 indicatethe reference position during the revolution period. The 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 1 SSREF + 0 1.0 µsec min. 1.37 µsec max. T = 0.0083 seconds ± 1.0% max ± 20 microseconds phase error while synchronized Figure 5. Synchronized reference signal characteristics