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190 Fibre Channel Interface Manual, Rev. D
12.10 Log Sense command
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 as inbound data of the Log Sense command.
The Log Sense command format that the initiator sends is shown in Table 122. The format of the data pages
sent back by the drive is shown in Table 123.
Field definitions (listed alphabetically)
Allocation Length
This field informs the drive of the amount of space available for returning log parameter data. If the allocation length is too
small, the drive sends as much data as can fit in the allocation length. The initiator can retrieve the rest of the log page
information by setting the parameter pointer to the last returned parameter code and reissuing the log sense command.
This process may be repeated as necessary to retrieve all the available information.
Control
See Control Bytes in Section 11.2.1.6.
Operation Code
4Dh The operation code for the Log Sense command.
Page Code
The page of data requested by the command (see Table 126). If a page code is sent that is not implemented, the drive ter-
minates the command with Check Condition status. The sense key is set to Illegal Request with the additional sense code
set to Invalid Field In CDB.
Table 127 (Page Code 00h) returns the list of log pages that the drive supports. This page is not defined for the Log Select
command.
PC (Page Control)
This field defines the type of log parameter the initiator selects to change with the Log Select command.
00b Log current threshold values
01b Log current cumulative values
10b Log default threshold values
11b Log default cumulative values
Table 122: Log Sense command (4Dh)
Bit
Byte
76543210
0
Operation Code (4Dh)
1 0 0 0 Reserved PPC SP
2 PC Page Code
3
Reserved
4
Reserved
5 (MSB)
Parameter Pointer
6 (LSB)
7 (MSB)
Allocation Length
8 (LSB)
9
Control
4Dh
Table
number
122
122
122
122
122