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 16/17 GCR decoder circuit based on the read data
(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.
(2)Programmable filter
The programmable filter circuit has a
(3)Adaptive equalizer circuit
This circuit is
(4)Viterbi detection circuit
The sample hold waveform output from the adaptive equalizer circuit is sent to the Viterbi detection circuit. The Viterbi detection circuit demodulates data according to the survivor path sequence.
(5)Data separator circuit
The data separator circuit generates clocks in synchronization with the output of the adaptive equalizer circuit. To write data, the VFO circuit generates clocks in synchronization with the clock signals from a synthesizer.
(6)16/17 GCR decoder
This circuit converts the
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