IBM IC25N020ATDA04 Hard Drive Specifications - Page 95

Power-off considerations, Load/Unload, Emergency unload

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11.3 Power-off considerations 11.3.1 Load/Unload Load/Unload is a functional mechanism of the HDD. It is controlled by the drive microcode. Specifically, unloading of the heads is invoked by the following commands. Command Standby Standby Immediate Sleep Response UL -> Comp. UL -> Comp. UL -> Comp. Reset Soft Reset Hard Reset Response Rdy (*1) UL -> Rdy "UL" -means "unload" "Rdy" -means "interface ready" (*1) Load/Unload condition is not changed by Soft Reset. Figure 63. Device behavior by ATA commands. Load/unload is also invoked as one of the idle modes of the drive. The specified start/stop life of the product assumes that load/unload is operated normally, NOT in emergency mode. 11.3.2 Emergency unload When HDD power is interrupted while the heads are still loaded, the microcode cannot operate and the normal 5V power is unavailable to unload the heads. In this case, normal unload is not possible, so the heads are unloaded by routing the back-EMF of the spinning motor to the voice coil. The actuator velocity is greater than the normal case, and the unload process is inherently less controllable without a normal seek current profile. Emergency unload is intended to be invoked in rare situations. Because this operation is inherently uncontrolled, it is more mechanically stressful than a normal unload. A single emergency unload operation is more stressful than 100 normal unloads. Use of emergency unload reduces the start/stop life of the HDD at a rate at least 100X faster than that of normal unload, and may damage the HDD. Travelstar 48GH, 30GN & 15GN hard disk drive specifications 81

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11.3 Power-off considerations
11.3.1
Load/Unload
Load/Unload is a functional mechanism of the HDD. It is controlled by the drive microcode. Specifically,
unloading of the heads is invoked by the following commands.
UL -> Comp.
Sleep
UL -> Comp.
Standby Immediate
UL -> Comp.
Standby
Response
Command
UL -> Rdy
Hard Reset
Rdy (*1)
Soft Reset
Response
Reset
Load/Unload condition is not changed by Soft Reset.
(*1)
—means "interface ready"
"Rdy"
—means "unload"
"UL"
Figure 63. Device behavior by ATA commands.
Load/unload is also invoked as one of the idle modes of the drive.
The specified start/stop life of the product assumes that load/unload is operated normally, NOT in emer-
gency mode.
11.3.2
Emergency unload
When HDD power is interrupted while the heads are still loaded, the microcode cannot operate and the
normal 5V power is unavailable to unload the heads. In this case, normal unload is not possible, so the
heads are unloaded by routing the back-EMF of the spinning motor to the voice coil. The actuator velocity
is greater than the normal case, and the unload process is inherently less controllable without a normal
seek current profile.
Emergency unload is intended to be invoked in rare situations. Because this operation is inherently
uncontrolled, it is more mechanically stressful than a normal unload.
A single emergency unload operation is more stressful than 100 normal unloads. Use of emergency
unload reduces the start/stop life of the HDD at a rate at least 100X faster than that of normal unload, and
may damage the HDD.
Travelstar 48GH, 30GN & 15GN hard disk drive specifications
81