DISK DRIVE OPERATION
SpinPoint P80
Product Manual Rev. 01
32
The read/write channel functions include a time base generator, AGC circuitry, asymmetry correction
circuitry (ASC), analog anti-aliasing low-pass filter, analog to digital converter (ADC), digital FIR filter,
timing recovery circuits, Viterbi detector, sync mark detection, 32/34 rate block code ENDEC, serializer and
de-serializer, and write pre-compensation circuits. Servo functions include servo data detection and PES
demodulation. Additionally the contains specialized circuitry to perform various parametric
measurements on the processed read signal. This allows for implementation of self-tuning and optimization
capability in every drive built using the .
A 9-bit NRZ interface is provided to support high speed data transfers to and from the controller.
Programming of the is performed through a serial interface. The serial interface is also used to
read various channel parameters that are computed on the fly.
5.2.3.1
Time Base Generator
The time base generator provides the write frequency and serves as a reference clock to the
synchronizer during non-read mode.
5.2.3.2 Automatic
Gain
Control
The AGC accepts a differential signal from the pre-amp, and provide a constant output
amplitude to the analog filter. It’s capable of accepting signal ranges from 40 mV to 400 mVppd.
5.2.3.3 Asymmetry
Correction
Circuitry
(ASC)
The ASC circuit is designed to correct for amplitude asymmetry introduced by MR heads. The
compensation range of this circuit is +/-45%. This circuit allows optimal bias current to be used
independent of the asymmetry effect.
5.2.3.4
Analog Anti-Aliasing Low Pass Filter
The 7
th
order equal-ripple analog filter provide filtering of the analog signal from AGC before it’s
being converted to digital signal with the ADC. It’s main function is to avoid aliasing for the
ADC circuit.
5.2.3.5
Analog to Digital Converter (ADC) and FIR
The output of the analog filter is quantified using a 6 bit FLASH ADC. The digitized data is then
equalized by the FIR to the NPV target response for Viterbi detection. The FIR filter consists of 7
independent programmable taps.