Fujitsu MHR2030AT User Manual download pdf (Page 62)

Theory of Device Operation

4-10 C141-E145-02EN

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 10 seconds.

If the error rate recovers to a value exceeding the specified value, self-calibration

is not performed.

4.6 Read/write Circuit

The read/write circuit consists of the read/write preamplifier (HDIC), the write

circuit, the read circuit, and the time base generator in the read channel (RDC).

Figure 4.4 is a block diagram of the read/write circuit.

4.6.1 Read/write preamplifier (HDIC)

HDIC equips a read preamplifier and a write current switch, that sets the bias

current to the MR device and the current in writing. Each channel is connected to

each data head, and HDIC switches channel by serial I/O. In the event of any

abnormalities, including a head short-circuit or head open circuit, the write unsafe

signal is generated so that abnormal write does not occur.

4.6.2 Write circuit

The write data is output from the hard disk controller (HDC) with the NRZ data

format, and sent to the encoder circuit in the RDC. The NRZ write data is

converted from 48-bit data to 50-bit data by the encoder circuit then sent to the

HDIC, and the data is written onto the media.

(1) 48/50 RLL MEEPRML

This device converts data using the 48/50 RLL (Run Length Limited) algorithm.

(2) Write precompensation

Write precompensation compensates, during a write process, for write non-

linearity generated at reading.

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Fujitsu MHR2030AT User Manual Page 62