Abstract: This invention relates to the structure of multiple registers used in image signal processing, and aims to simplify the register structure and to reduce the power consumption of the registers and the time required for testing an image signal processing LSI with the registers. A semiconductor integrated circuit according to the invention has a clock generation circuit and a clock buffer circuit for generating a plurality of clock signals, a register group including a plurality of registers connected in series and operable in synchronism with the clock signals, at least one combinational circuit connected to the register group, and means for selecting one of a normal operation mode and a scan test mode for the register group. The clock generation circuit receives a system clock CP.sub.IN, a scan test mode selection signal S.sub.MODEN, and clock CPS.sub.IN, and outputs a clock .phi. and a clock (.phi..sub.1 bar) controlled by the signal S.sub.