SCSI Description
Quantum Atlas 10K II Ultra160/m SCSI Hard Disk Drives 5–141
5.23 READ CAPACITY Command (25h)
The READ CAPACITY command reports formatted capacity and track-boundary
information.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (25h)
1 Reserved RelAdr
2 - 5 Logical Block Address
6 - 7 Reserved
8 Reserved PMI
9 Control
Figure 5–59 READ CAPACITY Command — Data Format
Table 5–66 READ CAPACITY Command — Field Descriptions
Field Description
RelAdr Relative Addressing is not supported by the drive; the field must be 0.
Logical Block Address Used in conjunction with the PMI bit. Must be 0 when the PMI bit is 0.
PMI Partial Media Indicator. When the value in the field is 0, the Returned
Logical Block Address (Figure 5-60) is that of the last logical sector of the
logical unit.
When the value is 1, the Returned Logical Block Address is that of the last
sector on the same cylinder as the Logical Block Address supplied in the
Command Descriptor Block's LBA field. That is, the Returned Logical Block
Address is that of the Logical Block Address before a substantial delay in
data transfer will be encountered).
In either case, Block Length in Bytes (Figure 5-60) is the unit's logical
sector size, as determined by the Block Length field in the Mode
parameter Block Descriptor.
