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LOG SENSE
Page Length: The Page Length field indicates the total number of bytes that follow this byte. The value returned
for this field depends on the value you specified for the Page Code and the Parameter Pointer in the CDB. This
value is independent of what you specified for the Allocation Length. A Page Length value that results in the
truncation of any parameter shall cause the target to terminate the command with CHECK CONDITION status.
The sense key shall be set to ILLEGAL REQUEST and the additional sense code shall be set to INVALID FIELD
IN PARAMETER LIST.
7.6.2.
The Log Parameter Descriptor
Most log pages contain one or more special data structures called log parameters. These may be data counters
which record the occurrence of certain events, or they may be more complex structures which describe activities
or other events which occur within the device. Each parameter structure begins with a 4-byte parameter header
followed by one or more bytes of parameter structure data. The 4-byte header is shown below:
Bit
7
Byte
0
(MSB)
1
2
DU (0)
3
4
n
Parameter Code: Identifies which parameter of data is being transferred. If the parameter code value is reserved
or not implemented by the target, then the target shall terminate the command with CHECK CONDITION status.
The sense key shall be set to ILLEGAL REQUEST and the additional sense code shall be set to INVALID FIELD
IN PARAMETER LIST.
The DU, DS, TSD, ET, TMC, and LP fields are collectively referred to as the control byte.
DU: The DU bit (Disable Update) is not defined for threshold values (indicated by the PC field of the LOG SENSE
command descriptor block). The target shall ignore the value of any DU bits in a LOG SELECT command.
DS: The DS bit informs the initiator that savable parameters are disabled (i.e. not supported), and should always
be 1. If it is 0 the command will terminate with CHECK CONDITION status with sense key set to ILLEGAL
REQUEST and additional sense code of ILLEGAL FIELD IN PARAMETER LIST.
TSD: A target save disable (TSD) bit of ZERO indicates a target-defined method for saving log parameters. This
implicit saving operation shall be done frequently enough to insure that the cumulative parameter values retain
statistical significance (i.e. across power cycles). A TSD bit of one indicates that either the target does not provide
a target-defined method for saving log parameters or the target-defined method has been disabled by the initiator.
If the initiator sets both the DS and the TSD bits set to one, the target shall terminate the command with CHECK
CONDITION status . The sense key shall be set to ILLEGAL REQUEST with the additional sense code set to
INVALID FIELD IN PARAMETER LIST.
ETC: An enable threshold comparison (ETC) bit of one indicates that when the cumulative parameter value is
updated, it shall be compared to the threshold parameter value and the action specified by the TMC field shall be
taken. An (ET) bit of ZERO disables this comparison. The ET bit is the same for both the cumulative and threshold
log parameter. Thus when the ET bit is set to a value by the initiator, this value is returned for both the cumulative
and threshold values of the log parameter.
TMC: The threshold met criteria (TMC) field defines the binary relationship between the cumulative and threshold
log parameter values under which the threshold is met. If the ET bit is one and the threshold condition is met, a
Unit Attention condition shall be posted to all initiators. When reporting the unit attention condition, the target shall
set the sense key to UNIT ATTENTION, the additional sense code to LOG EXCEPTION, and the additional sense
code qualifier to THRESHOLD CONDITION MET.
The TMC field is the same for both the cumulative and threshold parameter. Thus when the TMC field is set to a
value by the initiator, this value is returned for both cumulative and threshold values of the log parameter.
SONY AIT-2 Turbo drive SDX-570V series Ver.1.0
Table 7-13: LOG PAGE Parameter Descriptor
6
5
4
Parameter Code
DS (1)
TSD (0)
ETC (0)
Parameter Length (n-3)
Parameter Value
7. ATAPI Packet Command Specification
3
2
1
TMC (00)
Reserved
0
(LSB)
LP (0)
7-13
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