Seagate ST12450W, Руководство по эксплуатации продукта

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ST12450W/WD Product Manual, Rev. A 19
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 (page 04h) is used for
enabling and disabling spindle synchronization mode (see the
SCSI-2
Interface Product Manual). If the target fails to synchronize, it creates a unit
attention to all initiators. The sense key is set to Unit Attention and the
additional sense code is set to RPL Status Change.
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 RPL Status Change.
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 RPL Status Change.
You may operate the drive with a rotational skew when synchronized. The
rotational skew is applied in the retarded direction (lagging the synchronized-
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 of a 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’s translation of the digital offset values to physical rotational offsets
results in offset values whose phase error lies within the
±
20 microseconds
phase 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.