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12.21.8 Phy Event Counters log (log page 11h)
See Section 10.16.3 for a description of the Phy Event Counters feature
READ LOG EXT log page 11h is one page (512 bytes) in length. The first Dword of the log page contains information
that applies to the rest of the log page. Software should continue to process counters until a counter identifier with
value 0h is found or the entire page has been read. A counter identifier with value 0h indicates that the log page
contains no more counter values past that point.
Table 145 READ LOG EXT Log Page 11h data structure definition
Byte
7
6
5
4
3
2
1
0
0
Reserved
1
Reserved
2
Reserved
3
Reserved
…
…
n
Counter n Identifier
n+1
n+2
Counter n Value
n +
Counter n
Length
…
…
508
Reserved
509
510
511
Data Structure Checksum
Counter n Identifier
Phy event counter identifier that corresponds to Counter n Value. Specifies the particular event counter that is being
reported. The Identifier is 16 bits in length.
Valid identifiers are listed in.
Counter n Value
Value of the Phy event counter that corresponds to Counter n Identifier. The number of significant bits is determined
by Counter n Identifier bits 14:12 (as defined in Section 12.21.8.2). The length of Counter n Value shall always be a
multiple of 16-bits. All counters are one-extended. For example, if a counter is only physically implemented as 8-bits
when it reaches the maximum value of 0xFF, it shall be one-extended to 0xFFFF. The counter shall stop (and not
wrap to zero) after reaching its maximum value.
Counter n Length
Size of the Phy event counter as defined by bits 14:12 of Counter n Identifier.
The size of the Phy event counter shall be a multiple of 16-bits.
Data Structure Checksum
The data structure checksum is the 2’s complement of the sum of the first 511 bytes in the data structure. Each byte
shall be added with unsigned arithmetic and overflow shall be ignored. The sum of all 512 bytes of the data structure
will be zero when the checksum is correct.
Reserved All reserved fields shall be cleared to zero
12.21.8.1 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.
211
Hard Disk Drive Specification