Product Features
XL500S
24
RELEASED 10/21/10 (WD CONFIDENTIAL)
2679-701211-A06
3.12
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 be suitable. In the case of a 3.3V supply
for the same LED, the resistor would be 130 Ohm 5% 1/16W.
The pin corresponding to P11 shall be used for Active LED (see “Device Plug Connector Pin
Definitions” on page 13).
3.13
Fluid Dynamic Bearings (FDB)
Bearing design that incorporates a layer of high-viscosity lubricant instead of ball bearings in
the hard drive spindle motor. As an alternative to conventional ball bearing technology, FDB
designs provide increased non-operational shock resistance, speed control, and improved
acoustics.
3.14
Staggered Spinup and Activity Indication (SATA Power Pin 11)
SATA device power connector pin 11 (see “Standard Factory Connectors” on page 13) is
defined as a means by the host to DISABLE staggered spinup and it may also be used by the
device to provide the host with an activity indication. According to the SATA spec, "Staggered
Spin-up Disable and Activity Signal shall not be enabled at the same time."
3.14.1
Staggered Spinup
When multiple disks are installed in an enclosure, it is desirable to provide a simple
mechanism by which a subsystem controller can sequence hard drive initialization to minimize
the current load presented during power up. Staggered spinup provides this mechanism by
preventing the hard drives from spinning up until after successful PHY initialization (i.e., after
PHY enters DP7:DR_Ready state).
Staggered spinup is only applicable during initial power-up. If a drive is spun down using ATA
commands—as a result of having been placed in Standby or Sleep power modes, for
example—the drive shall spin up following the rules that govern spinup from low power modes
described in ATA/ATAPI-6 or later.
3.14.2
Activity Indication
The host controller through SATA power pin 11 may access storage device status and
activity. The signal provided by the device for activity indication is a low-voltage low-current
signal. It is not suitable for directly driving an LED. A buffer circuit external to the device must
be employed to drive the LED. The activity signal is based on an open-collector or open-drain
active low driver. The device shall tolerate the activity signal being shorted to ground.
3.15
CacheFlow™
CacheFlow is WD’s unique, multi-generation disk caching system. It incorporates read cache
with write cache.
WD designed CacheFlow to obtain maximum performance with today’s most popular
operating systems and applications. CacheFlow increases performance over prior caching
algorithms by increasing the number of times that requested data is in the cache. This reduces
