Specifications

5.6 Seagate standard power management commands

Many Seagate drives designed for portable or laptop computers imple-

ment power management using both ATA-standard and Seagate-spe-

cific commands. These commands switch the drive between the four

primary modes of operation as shown in Figure 9.

Note. An alternative set of power management commands were imple-

mented on some earlier Seagate drives, including the ST9051A,

ST9077A, ST351A/X and some versions of the ST3096A and

ST3120A. These are described in Section 5.7.

5.6.1 Active and Set Idle Timer command

This command (command code FB

) causes the drive to enter Active

mode. The time limit for automatic entry to Idle mode is also set by this

command. When the drive receives this command, it asserts Busy in the

Host Status register, initiates entry into Active mode, negates Busy, and

generates an interrupt.

If the drive was in Standby mode, it spins up to enter Active mode. The

drive does not wait for the spinup to be complete before generating the

interrupt. The Sector Count register is interpreted by this command as a

time interval in 100-msec increments to be used for automatic entry into

Idle mode.

The time interval set by this command is the maximum time that the drive

remains in Active mode between future commands received from the

host. A value of zero in the Sector Count register disables the timer used

for automatic entry to Idle mode.

5.6.2 Active Immediate command

When the drive receives this command (command code F9

), BSY is set

to 1 and the drive enters Active mode. If the drive is in Standby mode,

the spinup routine is executed. (If the drive is in either Active mode or

Idle mode, the spindle is already up to speed, and the spinup routine is

skipped.) Then, the drive clears BSY and generates an interrupt. This

interrupt is generated even if the drive is not fully in Active mode.

5.6.3 Check Idle Mode command

This command (command code FD

) checks the current power mode of

the drive. When the drive receives this command, it asserts Busy in the

Host Status register, indicates the current power mode in the Sector

Count register, negates Busy and generates an interrupt.

ATA Interface Reference Manual, Rev. C 59