Product Manual - Disc Drive SCSI-2/SCSI-3 Interface (Vol. 2; Ver. 2), Rev. E 119
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5.1.3.3
Log Sense Command (4Dh)[1]
The Log Sense command provides a means for an initiator to retrieve statistical information maintained by
the drive about the drive operation. It is a complementary command to the Log Select Command. This
information is stored in logs (counters) in the drive and is sent to the initiator in the data-in phase of the Log
Sense command. The Log Sense command format that the initiator sends is shown in Figure 5.1.3.3-1. The
format of the data pages sent back by the drive in the data-in phase is shown in Figure 5.1.3.2-3.
Table 5.1.3.3-1. The Log Sense Command (4Dh)
Bit
7
6
5
4
3
2
1
0
Byte(s)
0
Operation Code (4Dh)
1
0
0
0
Reserved
PPC
SP [2]
[1]
2
PC [3]
Page Code [4]
3
Reserved
4
Reserved
5
(MSB)
Parameter Pointer [5]
6
(LSB)
7
(MSB)
Allocation Length [6]
8
(LSB)
9
0
0
0
0
0
0 Flag [7]
Link [7]
[1]
Not supported by Standard OEM drives, but is a factory installed option.
Notes.
[1] Parameter Pointer Control (PPC). A PPC bit of one indicates that the drive shall return a log page with
only those log parameters that have changed since the last Log Select or Log Sense command. The
drive returns log parameter codes following (in ascending numerical order) the parameter code specified
in the Parameter Pointer (bytes 5 & 6—see note [5]).
A PPC bit of zero indicates that all of the log parameter data requested from the drive, whether changed
or not, is sent and it begins with the log specified by the parameter code given in the Parameter Pointer
field and returns the number of bytes specified by the allocation length field, in ascending order of param-
eter codes starting at the parameter code given in the Parameter Pointer field. A PPC bit of zero and a
Parameter Pointer field of zero causes all available log parameters for the specified log page to be
returned to the initiator subject to the allocation length.
[2] Save Parameters bit (SP). If SP bit is zero the drive performs the specified Log Sense command and
does not save any log parameters to non-volatile memory. If SP bit is one the drive first saves param-
eters identified as savable (by the DS bit in Table 5.1.3.2-4) to a nonvolatile location, and then performs
the rest of the Log Sense command.
[3] Page Control (PC). This field defines the type of drive log parameter the initiator requests the drive to
send back on the data-in phase. See Table 5.1.3.2-2 for definition of this field. The parameter values
returned on the data-in phase are from one of the following:
