Nxp 74hct series logic devices nxp smd74hct595d the 74hc595d is an 8 stage serial shift register with a storage register and 3 state outputs the registers have separate clocksdata is shifted on the positive going transitions of the shift register clock input shcp the data in each register is transferred to the storage register on a positive going transition of the storage register clock input stcp if both clocks are connected together the shift register will always be one clock pulse