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Western Digital Hard Disk Drive OEM Specification
9.17
Serial ATA Optional Features
There are several optional features defined in Serial ATA Revision 3.2. The following shows whether these features
are supported or not.
9.17.1
Asynchronous Signal Recovery
The device supports asynchronous signal recovery defined in Serial ATA Revision 3.2.
9.17.2
Device Power Connector Pin 11 Definition
Serial ATA Revision 3.2 specification defines that Pin 11 of the power segment of the device connector may be used
to provide the host with an activity indication and disabling of staggered spin-up.
9.17.3
Phy Event Counters
Phy Event Counters are an optional feature to obtain more information about Phy level events that occur on the
interface. This information may aid designers and integrators in testing and evaluating the quality of the interface. A
device indicates whether it supports the Phy event counters feature in IDENTIFY (PACKET) DEVICE Word 76, bit 10.
The host determines the current values of Phy event counters by issuing the READ LOG EXT command with a log
page of 11h. The counter values shall not be retained across power cycles. The counter values shall be preserved
across COMRESET and software resets.
The counters defined can be grouped into three basic categories: those that count events that occur during Data FIS
transfers, those that count events that occur during non-Data FIS transfers, and events that are unrelated to FIS
transfers. Counters related to events that occur during FIS transfers may count events related to host -to-device FIS
transfers, device-to-host FIS transfers, or bi-directional FIS transfers. A counter that records bi-directional events is
not required to be the sum of the counters that record the same events that occur on device-to-host FIS transfers
and host-to-device FIS transfers.
Implementations that support Phy event counters shall implement all mandatory counters, and may support any of
the optional counters as shown in Table 39. Note that some counters may increment differently based on the speed
at which non-Data FIS retries are performed by the host and device. Implementations may record CRC and
non-CRC error events differently. For example, there is a strong likelihood that a disparity error may cause a CRC
error. Thus, the disparity error may cause both the event counter that records non-CRC events and the event
counter that records CRC events to be incremented for the same event. Another example implementation difference
is how a missing EOF event is recorded; a missing EOF primitive may imply a bad CRC even though the CRC on the
FIS may be correct. These examples illustrate that some Phy event counters are sensitive to the implementation of
the counters themselves, and thus these implementation sensitive counters cannot be used as an absolute measure
of interface quality between different implementations.
9.17.3.1
Counter Reset Mechanisms
There are two mechanisms by which the host can explicitly cause the Phy counters to be reset.
The first mechanism is to issue a BIST Activate FIS to the device. Upon reception of a BIST Activate FIS the device
shall reset all Phy event counters to their reset value. The second mechanism uses the READ LOG EXT command.
When the device receives a READ LOG EXT command for log page 11h and bit 0 in the Features register is set to
one, the device shall return the current counter values for the command and then reset all Phy event counter values.
