Abstract: A system comprises an encoder, a precoder, a PRML channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies encoding such that the code string after passing through the precoder has a Hamming distance greater than one to eliminate error events with a small distance at the output of the PRML channel. The present invention also provides codes that after precoding have Hamming distance of 2 and 0 mod 3 number of ones. These codes when used over a PRML channel in an interleaved manner preclude +/-( . . . 010-10 . . . ) error events and error events +/-( . . . 01000-10 . . . ). The code string also has a predetermined minimum number of ones at the output of the PRML channel to help derive a clock from the input signal.

Abstract: A ring oscillator includes a set of metal-oxide-semiconductor (MOS) complementary, inverting stages, wherein each stage includes a pair of cross-coupled CMOS NAND or NOR gates. The first and last stages are also cross-coupled, such that positive and negative output signals of the last stage are connected respectively to negative and positive input signals of the first stage.

Abstract: A system and method includes an encoder and noise predictive Viterbi detector tuned such that error events with small values of the unique distance metrics are eliminated so that the error rate is enhanced. The system includes an encoder, a modulator, a PR channel and a detector. An input signal is input to the encoder. The encoder preferably encodes the input string with an even weight code to generate a code string thereby providing high code rates that are easy to implement. The output of the encoder is coupled to the input of the PR channel. The PR channel preferably comprises a filter and a noise source coupled to form a channel, a sampler, a low pass filter and an equalizer. The output of the channel is input to the low pass filter. The output of the low pass filter is coupled by the sampler to the input of the equalizer. Finally, the output of the equalizer is coupled to the input of the detector.

Abstract: A system comprises an encoder, a precoder, a PR channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies such encoding such that the code string after being modified by the precoder has a pre-selected parity structure. The encoder provides a systematic encoding scheme in which many of the encoded bits are the same as the input bits used to generate the encoded bits. This systematic approach of the present invention provides an encoder that is easy to implement because a majority of the bits are directly "feed through" and non-trivial logic circuits are only needed to generate the control bits. The systematic encoding also dictates a decoder that is likewise easy to construct and can be implemented in a circuit that simply discards the control bit.

Abstract: Write and read bias current control circuits are programmable through a control port. Both the read head bias DAC and the write DAC are controlled through a control port and both DACs use current as an input reference. The write and the read bias currents have constant reference current components which are set externally. The write and the read bias currents additionally have components which are a product of the reference current and a digital word loaded into an associated one of the DACs.