PURPOSE: To make level conversion possible by using a no-code operator by converting reference level data according to conversion level data.

CONSTITUTION: Data to be level-converted is denoted as S, reference level data as P, and conversion level data as G. Then, data after conversion is expressed by (1) (where each signal consists of eight bits). This is modified into expressions (2) and (3). For this purpose, data converter 11 that converts reference data P according to conversion data G converts conversion data G to obtain A of expression (4). This and converted data S are added together by no-code adder 12. Next, its sum is multiplied by conversion data G by no-code multiplier 13. Thus, the no-code operator is used for level conversion.