FUJITSU MHT2060AT - Manual (Page 64)

Theory of Device Operation
4-12 C141-E192-01EN
(3) FIR circuit
This circuit is 10-tap sampled analog transversal filter circuit that equalizes the
head read signal to the Modified Extended Partial Response (MEEPR) waveform.
(4) A/D converter circuit
This circuit changes Sampled Read Data Pulse from the FIR circuit into Digital
Read Data.
(5) 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.
(6) ENDEC
This circuit converts the 34-bit read data into the 32-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 30 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.