Fujitsu MPF3XXXAT manual Read/write preamplifier PreAMP, Write circuit, Read circuit

4.6Read/write Circuit

The read/write circuit consists of the read/write preamplifier (PreAMP), the write circuit, the read circuit, and the time base generator in the read channel (RDC).

4.6.1Read/write preamplifier (PreAMP)

One PreAMP is mounted on the FPC. The PreAMP consists of an 4-channel read preamplifier and a write current switch and senses a write error. Each channel is connected to each data head. The head IC switches the heads by the serial port (SDEN, SCLK, SDATA). The IC generates a write error sense signal (WUS) when a write error occurs due to head short-circuit or head disconnection.

4.6.2Write 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 with synchronizing with the write clock. The NRZ write data is converted from 48-bits data to 51-bits data by the encoder circuit then sent to the PreAMP, and the data is written onto the media.

(1)48/51 GCR

The disk drive converts data using the 48/51 group coded recording (GCR) algorithm.

(2)Write precompensation

Write precompensation compensates, during a write process, for write non-linearity generated at reading.

4.6.3Read circuit

The head read signal from the PreAMP is regulated by the automatic gain control (AGC) circuit. Then the output is converted into the sampled read data pulse by the programmable filter circuit and the adaptive equalizer circuit. This clock signal is converted into the NRZ data by the 48/51 GCR decoder circuit based on the read data maximum-likelihood-detected by the Viterbi detection circuit, then is sent to the HDC.

(1)AGC circuit

The AGC circuit automatically regulates the output amplitude to a constant value even when the input amplitude level fluctuates. The AGC amplifier output is maintained at a constant level even when the head output fluctuates due to the head characteristics or outer/inner head positions.

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