5.12MODE SELECT (6) Command (15h)

SCSI refers to the drive’s operational parameters as its mode parameters. SCSI groups the mode parameters by function into a set of data structures referred to as mode pages. The MODE SELECT (6) command allows the initiator to modify some of these mode pages and thereby control some of the drive’s operational characteristics. The Save Page (SP) option in the Command Descriptor Block makes the changes permanent. The new mode parameters are then stored in the drive’s non-volatile memory. The MODE SELECT CDB is described in Table 5-47and a description of the fields in Table 5-48.

Table 5-47MODE SELECT (6) Command Descriptor Block-Data Format

Bit

7

6

5

4

 

3

2

1

0

Byte

 

 

 

 

 

 

 

 

 

 

0

 

 

 

Operation

Code (15h)

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

Reserved

 

PF

 

 

Reserved

 

SP

 

 

 

 

 

 

 

 

 

 

2 – 3

 

 

 

 

Reserved

 

 

 

 

 

 

 

 

 

 

 

4

 

 

 

Parameter Length List

 

 

 

 

 

 

 

 

 

 

 

 

5

 

 

 

 

Control

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-48MODE SELECT (6) Command Field Descriptions

Data Field

Description

 

 

PF

Page Format. The drive ignores the content of this field and produces a mode

parameter list that contains a mode header optionally followed by a sector de-

 

scriptor and one or more pages that conform to the format shown here.

 

Save Pages. When SP = 0, the drive performs the specified MODE SELECT

SP

operation and does not save any pages. When SP = 1, the drive performs the

specified operation and stores all savable pages, (PS =1 on MODE SENSE re-

 

turn) including any sent during the data-out buffer transfer. The changes made

 

when SP = 1 become permanent changes to the drive’s SCSI setup.

Parameter List Length

This field tells the drive how many bytes of Mode Parameters to fetch in the

data-out buffer transfer. A CHECK CONDITION status is returned if this val-

 

 

ue truncates a page.

 

 

5.12.1Initiator-Changeable Mode Pages

Table 5-49lists the mode pages that are supported by the drive. An initiator can change these pages by supplying them, with the desired changes included, in the MODE SELECT command’s data-out buffer transfer.

The initiator should first use a MODE SENSE command to read the appropriate pages and leave non-changeable values as read when the initiator subsequently writes the changeable pages with the MODE SELECT command. If a non-changeable field contains an invalid value, the drive returns a CHECK CONDITION status.

5-34 Maxtor Atlas 10K V