Specifications

interrupt is generated even though the drive may not have completed its
transition to Idle mode.
If the Sector Count register is not zero, then the automatic power-down
sequence is enabled and the timer begins counting down immediately.
The duration of the standby timer depends on the value in the Sector
Count register, which is in units of 5 seconds (for example, 1 = 5 seconds
and 2 = 10 seconds). If the Sector Count register is zero, then the
automatic power-down sequence is disabled.
5.5.3 Idle Immediate command
This command (command codes 95
H
and E1
H
) causes the drive to set
BSY to 1, enter the Idle mode, clear BSY, and generate an interrupt. The
interrupt is generated even though the drive may not have completed the
transition to Idle mode.
5.5.4 Sleep command
This command (command codes 99
H
and E6
H
) is the only way to cause
the drive to enter Sleep mode. When entering sleep mode, the drive spins
down. After the spindle has stopped, the drive clears BSY, generates an
interrupt, and deactivates the interface. The only way to recover from
Sleep mode is by issuing a software reset or hardware reset.
A drive will not power-on in Sleep mode nor remain in Sleep mode
following a reset sequence.
5.5.5 Standby
This command (command codes 96
H
and E2
H
) causes the drive to enter
the Standby mode. The drive may return the interrupt before completing
the transition to Standby mode.
If the Sector Count register is not zero, then the automatic power-down
sequence is enabled and the timer begins counting down when the drive
returns to Idle mode. If the Sector Count register is zero, then the
automatic power-down sequence is disabled.
5.5.6 Standby Immediate
This command (command codes 94
H
and E0
H
) causes the drive to enter
the Standby mode. The drive may return the interrupt before completing
the transition to Standby mode.
58 ATA Interface Reference Manual, Rev. C