SCSI Description

Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–55

LOG SENSE Command (4Dh) (continued)
5.13.1 LOG SENSE Command Descriptor Block

The Command Descriptor Block for the LOG SENSE command is shown in Figure

5−21. Table 5–22 contains field descriptions.

Bit
Byte
7 6 5 4 3 2 1 0
0Operation Code (4Dh)
1Reserved PPC SP
2PC Page Code
3 – 4 Reserved
5 – 6 Parameter Pointer
7 – 8 Allocation Length
9Control

Figure 5–21 LOG SENSE Command Descriptor Block — Data Format

Table 5–22 LOG SENSE Command Descriptor Block — Field Descriptions

Field Description
PPC The Parameter Pointer Control bit controls the type of parameters that
can be requested from the drive. This bit must be 0, indicating that all
log parameters for the specified page (subject to the allocation length
specified) are returned to the initiator.
SP The Save Pages bit specifies whether the parameters are to be saved. This
bit must be 0, indicating that no parameters are to be saved and are reset
at power-on or by a TARGET RESET.
PC The Page Control field defines the type of parameter values to be
selected. The field must be 01b indicating that the current values are to
be returned. Mode 11b (return default values) is not supported because
all counters have a default value of 0.
Page Code The value specified as the Page Code determines the page to be returned.
Table 5−21 contains a list of supported log pages and their page codes.
Parameter Pointer This field is related to the PPC field. This bit must be 0.
Allocation Length This specifies the number of bytes of data that the drive is allowed to
pass during the DATA IN phase. The requested page is truncated if its
length exceeds the number of bytes specified in this field.