Read Capacity (25) - IBM DDRS-39130 - Ultrastar 9.1 GB Hard Drive Specifications

7.15 READ CAPACITY (25)

Byte
7 6
0
1 LUN
2 (MSB)
3
4
5
6
7
8
9 VU = 0
Figure 90. R E A D CAPACITY (25)
The READ CAPACITY command returns information regarding the capacity of the file.
Logical Block Address is used in conjunction with the PMI bit.
RelAdr. A Relative Address is not supported. Must be set to zero.
PMI, Partial Medium Indicator indicates;
PMI Description
0 The drive returns the last logical block address of the file.
1 The drive returns the last logical block address and block length in bytes are that of the
logical block address after which a substantial delay in data transfer will be encountered.
This returned logical block address shall be greater than or equal to the logical block address
specified by the RelAdr and logical block address fields in the command descriptor block.
This option provides the information the initiator needs to determine the amount of space
available on the same track which is accessible without a head switch or seek.
7.15.1.1 Returned Data Format
The data returned to the initiator in response to the R E AD CAPACITY command is described here. The
data is returned in the DATA IN phase.
Bit
5 4 3
Command Code = 25h
Reserved = 0
Logical Block Address
Reserved = 0
Reserved = 0
Reserved = 0
2 1 0
RelAdr
= 0
(LSB)
PMI
FLAG LINK
SCSI C O M M A N D SET
121