Seagate ST3285N, Product Manual, Page: 71 / 151

3.5 Group 1 commands
3.5.1 Read Capacity command (25
H
)
The initiator uses the Read Capacity command to determine the capacity
of the drive. When the drive receives the Read Capacity command, it
sends the initiator read capacity data, which is described in Sec-
tion 3.5.1.1.
Bit
Byte
7 6 5 4 3 2 1 0
0 0 0 1 0 0 1 0 1
1 LUN 0 0 0 0 Rel Adr
2–5 Logical block address
6 0 0 0 0 0 0 0 0
7 0 0 0 0 0 0 0 0
8 0 0 0 0 0 0 0 PMI
9 0 0 0 0 0 0 Flag Link
Bytes 2–5 The logical block address specified in the CDB cannot be
greater than the logical block address reported by the drive
in the read capacity data.
Byte 8 If the partial medium indicator (PMI) bit is zero, the logical
block address in the CDB is also zero. The read capacity
data returned by the drive contains the logical block address
and block length of the last logical block of the drive.
If the PMI bit is one, the drive returns the read capacity data,
which contains the logical block address and block length
of the last logical block address, after which a substantial
delay (approximately 1 msec) in data transfer occurs. This
logical block address must be greater than or equal to the
logical block address specified in the command descriptor
block. This reported logical block address is a cylinder
boundary.
ST3655 Family SCSI Drives Product Manual, Rev. A 61