THRESHOLD VALUE CONTROL SYSTEM IN A RECEIVER CIRCUIT

摘要

A threshold value control system for discriminating an input signal received by a receiver circuit, comprising a mode setting unit for determining a mode setting signal corresponding to a connection pattern of the receiver circuit; a variable threshold value generating unit for generating a variable threshold value which varies depending on the variation of the level of said input signal; a constant threshold value generating unit for generating at least one constant threshold value by which the level of the input signal can be discriminated even when its level cannot be distinguished by the variable threshold value; a threshold comparing unit for comparing the variable threshold value and each of the at least one constant threshold value to output a comparison result; a switching unit for passing only one of the variable threshold values and the at least one constant threshold value as an input digital signal discriminating threshold value, based on the mode setting signal output from the mode setting unit and the comparison result output from the threshold comparing unit, the input digital signal discriminating threshold value being sufficient to discriminate the digital level of the input signal; and a comparing unit for comparing the level of the input signal and the input digital signal discriminating threshold value to output a discriminated result, whereby bit errors or synchronization deviation can be prevented even when there is a superimposition of frame signals or noises.