5.40START STOP UNIT Command (1Bh)

The START STOP UNIT command enables or disables the logical unit for media access operations. This command gives the initiator remote control over drive spin- up and spin-down. The data format and field descriptions are shown in Table 5-199 and Table 5-200 respectively.

A jumper (or backplane connection) is used to select the spin-up mode. When configured for remote control of spin-up (Option 3), the drive requires a START STOP UNIT Command to spin up. See Chapter 3 for jumper-programming instructions for your specific hard disk drive.

Table 5-199START STOP UNIT Command Descriptor Block-Data Format

Bit

7

6

5

4

 

3

 

2

1

0

Byte

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

Operation

Code (1Bh)

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

 

 

Reserved

 

 

 

 

Immed

 

 

 

 

 

 

 

 

 

 

2 - 3

 

 

 

Reserved

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

Power Conditions

 

 

Reserved

 

LoEj

Start

 

 

 

 

 

 

 

 

 

 

 

5

 

 

 

Control

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5-200START STOP UNIT Command-Field Descriptions

Field

Description

 

 

 

Immediate. When 1, the drive returns GOOD status immediately after validating the

Immed

Command Descriptor Block, but before the drive spins up.

When 0, the drive does not return GOOD status until after the drive has spun up success-

 

 

fully and is ready for media access commands.

 

 

LoEj

Load Eject. This value must be zero, because the disk drive contains non-removable me-

dium.

 

 

When Start is 1, the unit spins up (if it is not currently spinning) and is left in a state where

Start

subsequent media access commands can succeed.

When the value is 0, the drive spins down. Subsequent media access commands are re-

 

 

jected with CHECK CONDITION status and the proper sense data.

 

 

Power

The Power Conditions field is not supported.

Conditions

 

5-144 Maxtor Atlas 10K V

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Maxtor 10K V manual Start Stop Unit Command 1Bh, 199START Stop Unit Command Descriptor Block-Data Format