SCSI Mode Sense Command
The SCSI Mode Sense command is used to obtain current device information from mode pages in a SCSI target device. There are two different versions of the command, a 6 byte version and a 10 byte version.
The CDB structure for the Mode Sense(6) command is:
bit→ |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
|---|---|---|---|---|---|---|---|---|
0 |
Operation code = 1Ah |
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1 |
LUN |
Reserved |
DBD |
Reserved |
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2 |
PC |
Page code |
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3 |
Reserved |
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4 |
Allocation length |
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5 |
Control |
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The CDB structure for the Mode Sense(10) command is:
bit→ |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
|---|---|---|---|---|---|---|---|---|
0 |
Operation code = 5Ah |
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1 |
Reserved |
LLBAA |
DBD |
Reserved |
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2 |
PC |
Page code |
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3 |
Reserved |
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4 |
Reserved |
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5 |
Reserved |
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6 |
Reserved |
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7–8 |
Allocation length |
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9 |
Control |
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The special control fields in the CDB have the following meaning:
- LLBAA - Long LBA Accepted - if "1" then the target is allowed to return parameter data with the LONGLBA bit set to "1"
- DBD - Disable Block Descriptors - if "1" then the target must not return any block descriptors
- PC - Page control -
- 00 - return current values
- 01 - return changeable values
- 10 - return default values
- 11 - return saved values
- Page Code - see the separate Wikipedia page for a list of mode pages