Maxtor 10K III manual $Vg, 5contains a description of the CDB control field, Naca

SCSI Description

Logical Block Address

The 6-byte READ, SEEK, and WRITE Command Descriptor Blocks

contain a 21-bit Logical Block Address. The 10-, 12-, and 16- Com-

mand Descriptor Blocks contain a 32-bit Logical Block Address.

Commands that require additional parameter data specify the length

of the Logical Block Address that is needed. See the specific com-

mand descriptions for more detailed information.

Relative Addressing indicates a technique used to determine the

next Logical Block Address to be operated on. The drive does not

support Relative Addressing, it defaults to a value of 0, which spec-

ifies that the Logical Block Address specifies the first logical block

of a range of logical blocks to be operated on by the command.

Transfer Length

The transfer length field normally specifies the number of sectors to

be transferred between the initiator and the drive. For several com-

mands, the transfer length indicates the number of bytes (not sec-

tors) to be sent. For these commands, this field may be identified

by a different name

Commands that use

for the transfer length value allow up

to 256 sectors of data to be transferred by one command. A trans-

fer length value of 0 indicates that 256 sectors are to be sent.

Transfer length values of 1 through 255 indicate the number of sec-

(KGNF

tors to be transferred.

&GUETKRVKQPfor the transfer length value

Commands that use

function differently. A transfer length value of 0 indicates that no

data transfer is to occur. Transfer length values of 1 or greater in-

dicate the number of sectors to be transferred.

Parameter List Length

The Parameter List Length is used to specify the number of bytes

sent during the data-out buffer transfer. This field is typically used

for parameters that are sent to a drive (for example, mode, diagnos-

tic, and log parameters). A parameter list length of 0 indicates that

no data is to be transferred.

Allocation Length

The Allocation Length field specifies the maximum number of bytes

that the initiator has allocated for returned data. The Allocation

Length is used to limit the amount of data returned to the initiator.

An Allocation Length of 0 indicates that no data is to be transferred

from the drive to the initiator. The drive terminates the data-in buff-

er transfer when the specified number of bytes have been trans-

ferred to the initiator or when all available data has been transferred,

whichever is less.

Control Field

The Control Field is the last byte of every Command Descriptor

Block; its format is shownQPG￿D[VGin Figure 5-2 and described in Table 5-3.

OWNVKRNG￿D[VGU

Typical

(6-Byte) Command Descriptor Block — Data Format

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-5contains a description of the CDB control field.

5-4 MaxtorTableAtlas5-410K III