User Manual

SCSI Commands Reference Manual, Rev. J 157

www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)

3.23 READ CAPACITY (16) command

3.23.1 READ CAPACITY (16) command overview

The READ CAPACITY (16) command (see table 121) requests that the device server transfer parameter data describing the capacity

and medium format of the direct-access block device to the data-in buffer. This command is mandatory if the logical unit

supports protection information and optional otherwise (see

SBC-4). This command is implemented as a service action of the

SERVICE ACTION IN operation code. This command may be processed as if it has a HEAD OF QUEUE task attribute.

LOGICAL BLOCK ADDRESS field and PMI bit

See 2.2.3 for the definition of the LOGICAL BLOCK ADDRESS field.

See the READ CAPACITY (10) command (see 3.22) for the definition of the PMI bit.

ALLOCATION LENGTH field

The ALLOCATION LENGTH field (see 2.2.6) specifies the maximum number of bytes that the application client has allocated for returned param-

eter data. An allocation length of zero indicates that no data shall be transferred. This condition shall not be considered as an error. The device

server shall terminate transfers to the data-in buffer when the number of bytes specified by the ALLOCATION LENGTH field have been trans-

ferred or when all available data has been transferred, whichever is less. The contents of the parameter data shall not be altered to reflect the

truncation, if any, that results from an insufficient allocation length.

Table 121 READ CAPACITY (16) command

Bit

Byte

7 6 5 4 3 2 1 0

OPERATION CODE (9Eh)

Reserved SERVICE ACTION (10h)

(MSB)

LOGICAL BLOCK ADDRESS (Obsolete)

. . .

(LSB)

(MSB)

ALLOCATION LENGTH

. . .

(LSB)

Reserved

PMI

(Obsolete)

CONTROL