Fujitsu 4.5.2 Execution timing of self-calibration, 4.5.3 Command processing during self-calibration

4.5 Self-calibration

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:

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In the case that the disk drive starts up normally, the first part of self- calibration starts after a lapse of 100 msec. The execution of first part is about 150 msec length. The remains is executed thereafter the transfer to Active-Idle state which takes about 200 msec.

The latter is interrupted when the disk drive receives a Host command, and it resumes after next transfer to Active-Idle state.

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-E280 4-9