START BIT DETECTION CIRCUIT

摘要

PURPOSE:To reduce the circuit scale by using a shift register for data serial/ parallel conversion in common use for a start bit detection shift register and constituting the circuit with a single shift register and a peripheral circuit of simple circuit constitution. CONSTITUTION:A 1st clock CLK1 is selectively outputted from a selector 12 and inputted to a shift register 11 and a start bit is serially inputted to a shift register 11, then a start bit discrimination circuit 13 applies its discrimination output to the selector 12 and a shift clock to the shift register 11 is switched into a 2nd clock CLK2. Thus, a data inputted to the shift register 11 serially just after the start bit is subject to bit-shift based on the 2nd clock CLK2 and extracted after serial/parallel conversion. Thus, the shift register 11 is used in common for both the start bit detection and data serial/parallel conversion to attain small-sized circuit constitution.