Fast data patterns with desired edge positions are provided. A pattern generator (PG) circuit 10 stores and provides data patterns and respective position control data. A delay circuit 16 delays a clock CLK to produce a position control clock according to the position control data. An output flip flop 18 provides the data patterns following to the position control clock. The position of the clock is controlled as an operation reference of the data pattern and, as a result, controls the edge positions of the output data pattern.