Product manual

The spindle-synchronization characteristics can be controlled by the

Mode Select command using the RPL bits in byte 17 of the Rigid Disc

Geometry page.

In the default mode, all drives arbitrate during startup to see which drive

will be the synchronized master. When the drives are calibrating their

heads, they each check for a reference signal pulse. The drive that

becomes ready first checks for the reference signal, and when it does

not detect a pulse, it takes over as the master and begins sending

reference pulses. All other drives synchronize their spindles to the

reference signal as they in turn become ready.

T1 Spindle clock period

13.34 msec ± 0.5%

T2 Duty cycle

0.5 µsec min

500 µsec max

T3 Spindle clock leading edge to

index leading edge

0 µsec ± 250 µsec

Spindle clock

Internal index

Figure 8. External spindle clock timing diagram

ST3655 Family SCSI Drives Product Manual, Rev. A 27