Moving reference channel quality monitor for read channels

摘要

The present invention provides a method and apparatus for monitoring a read channel in a disk drive system and calibrating the disk drive system. In one embodiment, a comparator circuit is provided to detect the data samples, that fall within a pre-programmed, variable-width distribution window. The output of the comparator circuit is digitized and sent to a logic block to qualify the valid samples. A relative counter or histogram of the detected data samples is obtained. The valid sample count is fed to a counter that can be accessed via a serial port. The channel parameters can be adjusted based upon a relative figure of merit read off the serial port that reflects the distribution of the samples with respect to the target value after processing a statistically valid number of samples. An embodiment of the invention provides a slicer circuit which generates an ideal waveform that tracks the input signal. The ideal waveform constitutes a moving reference for comparison with the sampled signal in a channel quality monitor. The moving reference signal reduces hardware requirements in the comparing circuitry of the channel quality monitor. Further, hardware utility is optimized in an embodiment by driving an AGC tuning loop, an LMS filter tuning loop, and a channel quality monitor circuit from the same slicer circuit.