Abstract: An on-chip data independent method and apparatus for channel error estimation in a data recovery scheme is based on measuring phase noise statistics. The apparatus (10) receives a data pulse and four quadrature clock signals and has a discriminating device (11) to provide a count signal for each data pulse received depending on which clock signal was the first to clock the particular data pulse. A pair of counters (12 and 13) counts the number of data pulses received at different phase offsets to provide a value representing a statistical ratio of the counts at different clock phase offsets from which an error rate for the received data pulses based on the counts at different clock phase offsets can be determined from a look-up table (16). By re-configuring the circuitry, the system can be adapted to measure clock window asymmetry.

Abstract: An on-chip data independent method and apparatus for channel error estimation in a data recovery scheme is based on measuring phase noise statistics. The apparatus (10) receives a data pulse and four quadrature clock signals and has a discriminating device (11) to provide a count signal for each data pulse received depending on which clock signal was the first to clock the particular data pulse. A pair of counters (12 and 13) counts the number of data pulses received at different phase offsets to provide a value representing a statistical ratio of the counts at different clock phase offsets from which an error rate for the received data pulses based on the counts at different clock phase offsets can be determined from a look-up table (16). By re-configuring the circuitry, the system can be adapted to measure clock window asymmetry.

Abstract: In a frequency control arrangement 200 of the type comprising an oscillator 270, a mark or space counter 210, a frequency detector 220 and an error signal calculator 230-260, 290 and in which it is desired to control the oscillator 270 to resonate at a frequency substantially equal to the frequency of a received data stream, the oscillator 270 is implemented as a four phase ring oscillator (FIG. 1, ref 110) arranged to provide phased clock signals to the mark or space counter (FIG. 1, ref 100). This allows the mark or space counter to be arranged to measure the length of the marks or spaces of the data with increased resolution.