Seagate ST15150N - Barracuda 4.3 GB Hard Drive Product Manual page 29

ST15150N/ND/W/WD/WC/DC Product Manual, Rev. D
SCSI interface factors
The Rotational Position Locking (RPL) field in byte 17 (bits 0 and 1) of the
Rigid Disc Drive Geometry mode parameters page 04h is used for enabling
and disabling spindle synchronization mode (see the SCSI-2 Interface
Product Manual). When the target achieves synchronization, it sends a Unit
Attention to all initiators. The sense key is set to Unit Attention and the
additional sense code is set to Spindles Synchronized (5C01).
After reaching synchronization, if the target detects a change of synchroni-
zation and:
1. If the logical unit is not executing an I/O process for the initiator, then the
target creates a unit attention condition. The sense key is set to Unit
Attention and the additional sense code is set to Spindles Synchronized
(5C01) or Spindles Not Synchronized (5C02).
2. If the logical unit is executing an I/O process and no other error occurs,
then the target returns Check Condition status. The sense key is set to
Recovered Error if the target is able to complete the I/O process or to
Hardware Error if the target is unable to complete the I/O process. The
additional sense code is set to Spindles Synchronized (5C01) or Spindles
Not Synchronized (5C02).
You may operate the drive may with a rotational skew when synchronized.
The rotational skew is applied in the retarded direction (lagging the synchro-
nized spindle master control). A rotational offset of up to 255/256 of a
revolution lagging may be selected. Select the amount of offset by using the
Mode Select command, Rigid Disc Drive Geometry page (page 04), byte 18
(see the SCSI-2 Interface Product Manual). The value in byte 18 (0–FFh) is
the numerator of a fractional multiplier that has 256 as the denominator. For
example, 40h selects 40h/FFh or 1/4 of a revolution lagging skew, 80h
selects 1/2 revolution lagging skew, etc. Since the drive supports all offset
values from 0 to 255, values sent by the initiator are not rounded off. The drive
translation of the digital offset values to physical rotational offsets results in
offset values whose phase error lies within the
error with respect to the supplied 120 Hz reference signal.
The drive does not have the capability to adjust the rotational offset value
requested by the initiator to a physical offset in the drive that corresponds in
any way to sector boundaries or changes in ZBR zones. The initiator must
formulate these boundaries or changes, if required, to calculate the value of
offset it sends to the drive.
19
20 microseconds phase