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To compensate torque constant value change depending on cylinder, whole
cylinders from most inner to most outer cylinder are divided into 13 partitions at
calibration in the factory, and the compensation data is measured for
representative cylinder of each partition. This measured value is stored in the SA
area. The compensation value at self-calibration is calculated using the value in
the SA area.
4.5.2 Execution timing of self-calibration
Self-calibration is performed once when power is turned on. After that, the disk
drive does not perform self-calibration until it detects an error.
That is, self-calibration is performed each time one of the following events occur:
When it passes from the power on for about 10 seconds except that the disk
•
drive shifts to Idle mode, Standby mode, and Sleep mode by execution of any
commands.
The number of retries to write or seek data reaches the specified value.
•
The error rate of data reading, writing, or seeking becomes lower than the
•
specified value.
4.5.3 Command processing during self-calibration
This enables the host to execute the command without waiting for a long time,
even when the disk drive is performing self-calibration. The command execution
wait time is about maximum 72 ms.
When the error rate of data reading, writing, or seeking becomes lower than the
specified value, self-calibration is performed to maintain disk drive stability.
If the disk drive receives a command execution request from the host while
performing self-calibration, it stops the self-calibration and starts to execute the
command. In other words, if a disk read or write service is necessary, the disk
drive positions the head to the track requested by the host, reads or writes data,
and then restarts calibration after about 3 seconds.
If the error rate recovers to a value exceeding the specified value, self-calibration
is not performed.
C141-E249
4.5 Self-calibration
4-9
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