FUJITSU MHD2032AT - Manual (Page 62)

4.6 Read/write Circuit
C141-E050-02EN 4-13
(3) Flash digitizer circuit
This circuit is 10-tap sampled analog transversal filter circuit that cosine-equalizes
the head read signal to the partial response class 4 (EPR4) waveform.
(4) Viterbi detection circuit
The sample hold waveform output from the flash digitizer circuit is sent to the
Viterbi detection circuit. The Viterbi detection circuit demodulates data according
to the survivor path sequence.
(5) 16/17 GCR decoder
This circuit converts the 17-bit read data into the 16-bit NRZ data.
4.6.4 Digital PLL circuit
The drive uses constant density recording to increase total capacity. This is
different from the conventional method of recording data with a fixed data transfer
rate at all data area. In the constant density recording method, data area is divided
into zones by radius and the data transfer rate is set so that the recording density
of the inner cylinder of each zone is nearly constant. The drive divides data area
into 12 zones to set the data transfer rate.
The MPU transfers the data transfer rate setup data (SD/SC) to the RDC that
includes the Digital PLL circuit to change the data transfer rate.