Hot Plug Support; Active Led Status - Western Digital Purple PR1000M Technical Reference Manual

P F
RODUCT EATURES
Preamp Thermal Asperity Compensation – A Thermal Asperity (TA) is a baseline shift in
the readback signal due to heating of the magnetoresistive stripe on the head as a
result of physical contact with the disk or a particle. The preamp circuit has the ability
to detect and compensate for thermal asperities. When an error cannot be corrected
by ECC On-the-Fly, another retry is performed, where the preamp with its thermal
asperity detection feature determines if the error is due to a thermal asperity. Once
the preamp determines that the error is due to thermal asperity, preamp
compensation is enabled. If preamp compensation alone is not enough to recover,
then the channel performs a series of TA-specific recoveries.
Read/Write Retry Procedure – This retry procedure is used by all disk controller error
types. If the procedure succeeds in reading or writing the sector being tried, then
recovery is complete and the controller continues with the command. Each retry
operation also checks for servo errors. The procedure ends when error recovery is
achieved or when all possible retries have been attempted.
Extended Read Retry Procedure – This retry procedure tries combinations of
positive/negative track offsets and data DAC manipulations to recover the data. This
retry procedure applies only to read data recovery. The Read/Write Retry procedure
performs the actual retry operation.
When an extended retry operation is successful, the controller continues with the
command. The controller clears any changes in track offset or data DAC settings
before the command continues.
3.17

Hot Plug Support

SATA supports hot plugging (also known as "hot swapping"), the ability to swap out a
failed hard drive without having to power down the system or reboot. This capability
contributes to both data availability and serviceability without any associated
downtime, making it a critical feature for extending SATA into enterprise applications.
These WD hard drives support SATA 2.5 hot plugging only in systems where a SATA
hard drive storage backplane is used.
The Serial ATA revision 2.5 specification requires staggered pins for both the hard
drive and drive receptacles. Staggered pins mate the power signals in the
appropriate sequences required for powering up the hot plugged device. These pins
are also specified to handle in excess of the maximum allowed inrush current that
occurs during drive insertion. SATA-compliant devices thus need no further
modification to be hot pluggable and provide the necessary building blocks for a
robust hot plug solution, which typically includes:
Device detection even with power downed receptacles (typical of server

applications).
Pre-charging resistors to passively limit inrush current during drive insertion.

Hot plug controllers to actively limit inrush current during drive insertion.

3.18

Active LED Status

The drive supports external LED requirements. It provides an activity LED output
which is ON during command execution and OFF otherwise.
The drive strength of this open Drain Drive Active signal is that it can sink 12mA to
0.4V Max. It is 5V tolerant, meaning that the external LED may be driven from +5V or
+3.3V so long as the Host system provides a series resistor to limit the LED current to
the lower of 12mA or the rated operating current of the LED. As an example with +5V
and a 2 volt forward drop across a 10mA LED, a 300 Ohm 5% 1/16W resistor would
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RELEASED 5/8/17 (WD CONFIDENTIAL)
PR1000M
2679-800020-A03