Maxtor 10K III manual Msb, Lba

SCSI Description

￿￿￿ %QOOCPFAn initiator￿&GUETKRVQTcommunicates￿$NQEMwith the drive by sending a 6-,10-, or 12-byte Command Descriptor Block (CDB) that contains the parameters for the specific command. The SCSI command's operation code is always the first byte in the CDB and a control field is the last byte. For some commands, the CDB is accompanied by a list of parameters sent during the data-out buffer transfer. Table 5-2shows the format of a typical six- byte CDB.

Typical (6-Byte) Command Descriptor Block-Data Format

0

Operation Code

1

Reserved

(MSB)

Logical Block Address

(LBA)

2 - 3

Logical Block Address

(LBA)

4

Transfer Length, Parameter List Length, or Allocation Length

5 Table5-2

Control

Reserved fields in CDBs and Parameters have a value of 0; Re-

served fields in states and other parameters sent to an initiator are

set to 0.

5-3contains a description of the CDB fields.

5-4describes the data format for a typical CDB.

$[VG$KV

￿

￿￿￿Command Descriptor Block-Field￿￿￿Descriptions

￿

Operation(KGNFCode

The first byte of a SCSI CDB&GUETKRVKPcontains an operation code. The oper-

Note:

Table5-3

ation code of the CDB has a

Qfield (bits 7-5) and a

field (bits 4-0). The 3-bit Group Code field provides%QOfor￿

eight groups of command codes. The 5-bit Command Code field

provides for 32 command codes in each group. A total, therefore,

of 256 possible operation codes exist. Operation codes are defined

in the SCSI command standards. The group code for CDBs specified

therein correspond to the length of the command descriptor as be-

low:

Group Code

Meaning

0

6-byte commands

1

10-byte commands

2

10-byte commands

3

Reserved

4

16-byte commands

5

12-byte commands

6

Vendor specific

7

Vendor specific

The operation code specifies the command being requested. The list

of supported SCSI commands and their operation codes are con-

tained in Table 5-1.

)TQWR￿%FG

OCPF￿%QFG

Maxtor Atlas 10K III

5-3