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OEM FUNCTIONAL SPECIFICATION ULTRASTAR XP (DFHC) SSA MODELS 1.12/2.25 GB - 1.0" HIGH
5.7 Spindle Synchronization
5.7.1 Synchronization overview
Spindle synchronization of drives is achieved by one node transmitting a special Sync character or a Sync
pulse once per every revolution of its drive. The transmitting is done either on SSA Link (sending Sync
character) or on a hard-wire (Sending Sync pulse) that connects all the drives via the SSA Option Port
'Sync' pin. The synchronization mode is controlled by the RPL field of the Mode Select Page 04h parameter
(see Ultrastar XP (DFHC) SSA Models Interface Specification for more details). The drive can operate in
one of three modes:
5.7.2 Synchronization Mode
Mode Operation
No Sync Spindle synchronization is disabled.
Slave Sync Spindle synchronization is attempted by synchronizing the spindle motor to the Sync
special character on SSA link (or the Sync pulse on Sync hard-wire) that is driven by
another node.
Master Sync Spindle synchronization is not attempted by this device. It generates a Sync special
character via SSA link (or a Sync pulse via a hard-wire) once per its spindle revo-
lution.
Master Sync Control Master Sync Control is not supported.
5.7.3 Synchronization time
It will take 6 seconds to synchronize the Slave drive to the Master drive. While the Slave drive is synchro-
nizing to these characters, it is not able to read or write data. Once synchronized the drive will maintain ±
20 microseconds synchronization tolerance.
When operating in Slave Sync mode, the drive must receive the Spindle Sync special characters at a period of
8.333 milliseconds with a tolerance of ± .025% (2.08 microseconds).
5.7.4 Synchronization with Offset
The Rotational Offset value is the amount of rotational skew that the Target uses when synchronized. The
rotational skew is applied in the retarded direction (lagging the synchronized spindle master control). The
value in the field is the numerator of a fractional multiplier that has 256 as its denominator (e.g., a value of
128 indicates a one-half revolution skew). A value of 00h indicates that rotational offset is not used. The
rotational offset is only used when the Drive is running in the Slave Sync RPL mode.
5.7.5 Synchronization Route
5.7.5.1 Over SSA Link
Spindle Sync special characters are forwarded from one SSA link to the other with a delay of 350
nanoseconds with a tolerance of ± 50 nanoseconds. This delay can be increased by 50 nanoseconds when
the drive is sending the second of a double character sequence (RR or ACK) and by 50 nanoseconds when
sending a SAT or SAT' character.
Source filename=SYNC IBM Corporation Page 69 of 87