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Fibre Channel Interface Manual, Rev. D 275
12.27 Read Capacity (16) command
The Read Capacity (16) command provides a means for the application client to request information regarding
the capacity of the block device. This command is implemented as a service action of the Service Action In
operation code.
Table 180: Read Capacity (16) command (9Eh)
Field definitions (listed alphabetically)
Allocation Length
Specifies the number of bytes the initiator has allocated for the returned defect data. An Allocation Length of zero indicates
that no Read Defect Data is transferred. Any other value indicates the maximum number of bytes to be transferred. The
drive terminates the Data In phase when the Allocation Length bytes have been transferred or when all available defect
data has been transferred to the initiator, whichever is less.
Control
See Control Bytes in Section 11.2.1.6.
Logical Block Address
The logical block address field specifies the first logical block of the range of logical blocks for this command.
PMI (Partial Medium Indicator)
0 The information returned in the Read Capacity data is the Logical Block Address and Block Length (in bytes) of the
last logical block of the logical unit. (This value is the same for all drives of the same model number, sector size and
sparing scheme. It is the same regardless of the number of defective blocks the drive has.) The Logical Block
Address in the Command Descriptor Block is set to zero (0) for this option.
Bit
Byte
76543210
010011110
1 Reserved Service Action (10h)
2
Logical Block Address (MSB)
3
Logical Block Address
4
Logical Block Address
5
Logical Block Address
6
Logical Block Address
7
Logical Block Address
8
Logical Block Address
9
Logical Block Address (LSB)
10
Allocation Length (MSB)
11
Allocation Length
12
Allocation Length
13
Allocation Length (LSB)
14 Reserved RelAdr PMI
15
Control
9Eh
Table
number
180
180
180
180