Patent attributes
A comparator circuit outputs a comparison result obtained by comparing a data signal with a threshold whose magnitude is adjusted based on a first offset value at a timing synchronized with a second clock signal whose phase is adjusted based on a difference in phase between the data signal and a first clock signal and a second offset value. An eye monitor circuit thins comparison results obtained in a clock data recovery (CDR) circuit for individual symbols of the data signal by comparing the data signal with a threshold, selects a comparison result corresponding to a symbol for which the comparison result is obtained by the comparator circuit, determines, by comparing the selected comparison result with the comparison result obtained by the comparator circuit, whether or not an error has occurred due to the first or second offset value, and outputs the number of times the error has occurred.
