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4.6 Read/write Circuit
C141-E042-01EN 4-13
(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) 8/9 GCR decoder
This circuit converts the 9-bit read data into the 8-bit NRZ data.
4.6.4 Time base generator 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 13 zones to set the data transfer rate. Table 4.3 describes
the data transfer rate and recording density (BPI) of each zone.
Table 4.3 Write clock freqeuncy and recording density (BPI) of each zone
Zone 0 1 2345
Cylinder 0
to
295
296
to
445
446
to
809
810
to
1455
1456
to
2080
2081
to
2605
Transfer rate
[MB/s]
8.92 8.92 8.71 8.29 7.88 7.54
Zone 6 7 8 9 10 11 12
Cylinder 2606
to
3137
3138
to
3888
3889
to
4238
4239
to
4823
4824
to
5400
5401
to
5873
5874
to
6371
Transfer rate
[MB/s]
7.19 6.67 6.44 6.04 5.63 5.29 4.93
The MPU transfers the data transfer rate setup data (SDATA/SCLK) to the RDC
that includes the time base generator circuit to change the data transfer rate.