PURPOSE: To count clocks at a high speed after a data is inputted.

CONSTITUTION: A shift register SR is in feedback connection and a data at an 8-th shift register 3H is given to a 5-bit counter 4 as a count object. A data to the shift register SR is shifted by each clock 1 and 3-bit outputs 8A, 8B, 8C of an encoder 20 are changed in response to the clock 1. The data to the shift register SR is shifted and circulated and every time the data is given to the 8-th shift register 3H, the 5-bit counter 4 is incremented and counts 8D, 8F, 8G, 8H in 5 bits of the 5-bit counter 4 are changed in response to the data of the shift register 3H. Then an 8-bit count data is obtained.