Disk Drive Operation
5-
12 WA31273A / WA32543A / WA33203A / WA32163A / WA31083A /
Dual
Level
Qualifier
Filter
Equalizer
Viterbi
Qualifier
AGC
Pre-Amp
&
Write Driver
Servo
Demodulato
r
Data
Separator
ENDEC
AT
Controller
Servo
Controller
Read/Write IC
SSI 32P4910BP
HDA
Figure 5-2. Read/Write (SSi32P4910BP) Block Diagram
5-2-2-2 Filter/Equalizer
The filter section provides low pass filtering, boost, and differentiation. Equalizer is used for the fine
shaping of the incoming read signal to the PR4 wave shape up to 7dB.
5-2-2-3 Pulse Qualifier
During servo reads this qualifier provides the qualified servo pulse and the polarity of the pulse.
During data reads this qualifier is used for ensuring pulse polarity changes during VCO sync field
counting.
The viterbi qualifier is only used during data read mode after the sync field count has been achieved.
This qualifier has two significant blocks, one that feeds the other. The first block is the sampled pulse
detector, it performs the pulse acquisition/detection in the sampled domain. It acquires pulses by
comparing the code clock sampled level of the analog waveform to the positive and negative
thresholds established by the programmable viterbi threshold window. After the pulses have been
detected they must be further qualified by the survival sequence registers and associated logic.
5-2-2-2 Data Separator
