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10.3.2 Power Management Commands
The Check Power Mode command allows a host to determine if a device is in, going to or leaving Standby or Idle
mode.
The Idle and Idle Immediate commands move a device to Idle mode immediately from the Active or Standby modes.
The Idle command also sets the Standby timer count and enables or disables the Standby timer.
The Standby and Standby Immediate commands move a device to Standby mode immediately from the Active or
Idle modes. The Standby command also sets the Standby timer count and enables or disables the Standby timer.
The Sleep command moves a device to Sleep mode. The device’s interface becomes inactive after the device reports
command completion for the Sleep command. A device only transitions from Sleep mode after processing a hardware
reset or a software reset.
10.3.3 Standby Timer
The Standby timer provides a method for the device to automatically enter Standby mode from either Active or Idle
mode following a host programmed period of inactivity. If the device is in the Active or Idle mode, the device waits for
the specified time period and if no command is received, the device automatically enters the Standby mode.
If the value of SECTOR COUNT Register on Idle command or Standby command is set to 00h, the Standby timer is
disabled.
10.3.4 Interface Capability for Power Modes
Each power mode affects the physical interface as defined in the following table:
Table 34 Power conditions
Mode
BSY
RDY
Interface active
Media
Active
x
x
Yes
Active
Idle
0
1
Yes
Active
Standby
0
1
Yes
Inactive
sleep
x
x
No
Inactive
Ready (RDY) is not a power condition. A device may post ready at the interface even though the media may not be
accessible.
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Hard Disk Drive Specification