Constellation CS Serial ATA Product Manual, Rev. C
13
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2.8.4
Power-management modes
The drive provides programmable power management to provide greater energy efficiency. In most systems, you can control
power management through the system setup program. The drive features the following power-management modes:
• Active mode
The drive is in Active mode during the read/write and seek operations.
• Idle mode
The buffer remains enabled, and the drive accepts all commands and returns to Active mode any time disk access is
necessary.
• Standby mode
The drive enters Standby mode when the host sends a Standby Immediate command. If the host has set the standby timer,
the drive can also enter Standby mode automatically after the drive has been inactive for a specifiable length of time. The
standby timer delay is established using a Standby or Idle command. In Standby mode, the
drive buffer is enabled, the
heads are parked and the spindle is at rest. The drive accepts all commands and returns to Active mode any time disk
access is necessary.
• Sleep mode
The drive enters Sleep mode after receiving a Sleep command from the host. In Sleep mode, the drive buffer is disabled,
the heads are parked and the spindle is at rest. The drive leaves Sleep mode after it receives a Hard Reset or Soft Reset
from the host. After receiving a reset, the drive exits Sleep mode and enters Standby mode with all current translation
parameters intact.
• Idle and Standby timers
Each time the drive performs an Active function (read, write or seek), the standby timer is reinitialized and begins counting
down from its specified delay times to zero. If the standby timer reaches zero before any drive activity is required, the drive
makes a transition to Standby mode. In both Idle and Standby mode, the drive accepts all commands and returns to Active
mode when disk access is necessary.
Power modes
Heads
Spindle
Buffer
Active
Tracking
Rotating
Enabled
Idle_a
ID Biased
Rotating
Enabled
Idle_b
Parked
Rotating
Enabled
Idle_c
Parked
Rotating at lower RPM
Enabled
Standby
Parked Stopped
Enabled
Sleep
Parked
Stopped
Disabled